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or TI1K 

University of California. 


Pacific Theological Seminary. 

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rtF THE 









In preparation by Professor BfllfnuTi, 

An Elementary Treatise on Natural Philosophy, for Colleges 

and Schools. 

Entered aeoording to the Act of Congress, in the year 1862, by 


in the Clark's Office of the District Conrt of the Eastern .Pktriet ot 

NvcasormD bt l. johwbok and a* 






itnjamin Silliman, 

fob nm tears professor of chemistry nc talk collbbb, 

Ii)i$ DolqftK» 











Ddbuto the fire years which hare passed since the second edition of 
this work was prepared, intense activity has prevailed in all depart- 
ments of chemical research. Any attempt to preserve the stereotype 
plates of that edition in the present was found to he quite impracti- 
cable. The whole work has been entirely revised, rewritten, and so far 
rearranged, as experience has shown to he desirable. Some parts have 
been enlarged, and some have been contracted, so that on the whole the 
size of the volume remains much as before. A great number of new 
illustrations have been added, more than doubling the number in the 
former editions. A considerable number of wood outs have been taken 
from Begnault's excellent Chun de Chimie, and many new ones have been 
drawn from the author's apparatus. Every important fact, formula, and 
number in the work has been carefully compared with the most recent and 
valued authorities. The changes made in the atomic weights of element- 
ary substances, during the last five years, have been numerous and im- 
portant; and in most oases these changes have added simplicity to the 
science. The new facts and principles gleaned in no inconsiderable num- 
bers for this edition, have been woven into the text in such a manner as 
to present, it is hoped, an uniformity of design. 

In v the Organic Chemistry, greater simplicity and unify has been 
giver. U> the principles involved in the almost unwieldy mass of facts 
which have accumulated so rapidly during the last ten years. The 
author has again to acknowledge his obligations to his friend and former 
associate, Mr. Hunt, for his lucid and original exposition of this part of 
the subject 

The adoption of this work by many of the first seminaries of learning 
in this country, is a gratifying evidence to the author that his design 
has been appreciated; and he trusts that those who gave their confi- 
dence to the two first editions, will find the present one, in many import- 
ant respects, superior to them. 

Hiw Havsh, September 80, 1862. 







The object of this work is sufficiently indicated by iti title. It hai 
grown out of the exigencies of teaching, and has been received as the 
text-book in the public lectures at Tale College. 

It is important that a work of this kind should contain only such 
matter as is actually taught to a class by recitations and lectures. 
All fulness beyond this is unavailable to either teacher or pupil, and 
serves often to embarrass the one and discourage the other. This is, 
perhaps, the reason why several works, otherwise excellent, have failed 
to answer the purpose for which they were written. The science of 
Chemistry has now reached the point where its first principles can be 
presented by the teacher with almost mathematical precision. 

Chemistry has attractions of an economical and experimental charac- 
ter, which will always secure for it a place in every system of educa- 
tion. Without wishing to diminish its claims to attention on these 
grounds, the author urges the paramount advantages possessed by his 
favourite science, as a study peculiarly fitted to train the mind to a me- 
thodized and logical habit of thought. If nothing more is to be derived 
from its study than the entertainment offered by brilliant phenomena, 
and a knowledge of convenient economical processes, the pupil will fail 
of its most important advantage. The beautiful philosophy, the perspi- 
cuous nomenclature, and lucid method of modern chemistry, are so ob- 
vious that they cannot fail to awaken the attention of every intelligent 
pupil, and carry him on his course of intellectual culture with rapid 

The author has consulted all the best authorities within his reach, 
both in the standard systems of England and France, and in the scien- 
tific journals of this country and Europe. The works of Daniell, Gra- 
ham, Brande, Kane, Fownes, Gregory, Faraday, Mitscherlich, Berselius, 
Dumas, LieMg, and Gerhardt, have all been used, as also the treatises 
of Dr. Hare and Prof. SiUiman. 

The Organic Chemistry is presented mainly in the order of Liebig in 
his Traite de Chimie Organique. The author takes pleasure in ac- 
knowledging the important aid derived in this portion of the work 
from his friend and professional assistant, Mr. TfiOMAS S. Hvht, whose 
familiarity with the philosophy and details of Chemistry, will not fail to 
make him one of its ablest followers. The labour of compiling the Or- 
ganic Chemistry has fallen almost solely upon him. 

If it shall be found to meet the wants of both teachers and pupils, and 
to promote the progress of Scientific Chemistry in this country, the 
author will feel that he has not laboured in vain. 

Nsw H&vnr, December 80, 1840. 








Sources of Natural Know- 

ledge 13 

Observation 14 

Divisions of Natural Science. 15 
MiniR.- General Properties 

of Matter 16 

Mechanical Attraction 17 

Molecules 18 

Three States of Matter— Co- 

hesion 19 

Capillary Attraction 21 

Exosmose and Endosmose..... 23 
Mechanical Properties of the 

Atmosphere 23 

Air-pumps 24 

Law of Mariotte 26 

Barometer , 28 

Weight of Atmosphere 30 

Weight and Specific Gravity 31 

Hydrometer...* 33 

Crystallization. — Nature of 

Crystallization 36 

Polarity of Molecules 37 

Crystalline Forms 9% 

Measurement of Crystals 41 

Light. — Sources and Nature... 43 

Undulations 44 

Properties of Light 46 

Reflection 47 

Simple Refraction 48 

Analysis of Light 50 

Double Refraction 52 

Polarisation 53 

Chemical Rays 55 

Phosphorescence 66 

Heat. — Sources » 6T 

Properties 68 

Communication of Heat 69 

Radiation 60 

Conduction « . 61 

Vibrations 62 

Convection , 65 

Transmission of Heat 66 

Expansion 69 

Thermometer 75 

Pyrometer 78 

Capacity for Heat 79 

Change of State produoed by 

Heat 81 

Liquefaction, Latent Heat... 82 

Vaporization 85 

Boiling 86 

Spheroidal State 87 

Boiling in vacuo 89 

Elevation of Boiling-points 

by Pressure ..» 90 

Steam Engine 92 

Evaporation 93 

Density of Vapors 94 

Dew-point 95 

Hygrometers 96 

Diffusion and Effusion of 

Gases 97 

Liquefaction and Solidifica- 
tion of Gases 98 

Electricity * 100 

Magnetic Electricity, Mag- 
netism 101 

Electrical Machines 107 

Statical Electricity 108 

Electroscopes 108 

Digitized by VjOOQ IC 



Theories of Electricity. ,- 110 

Leyden Jar Ill 

Eleotrophoruf 113 

Galvanism 114 

Voltaic Pile 115 

Ohm's Law 118 

Batteries 120 

Smee's Battery 121 

Daniell's Battery 122 

Grove's Battery. » 123 

Bunsen's Battery 124 

Electrical Light 125 


Electro-Magnetism .. » 127 

Amperes Theory- 128 

Electro-Magnets. 130 

Electromagnetic Telegraph.. 131 
Pro£ Henry's Discoveries.... 134 

Magneto-Electricity 137 

Thermn-Electricity 139 

Animal Electricity 140 

Electrochemical Decomposi- 
tions 142 

Faraday's Researches 143 

Electrotype. M 148 

PART n. 


elements ahd thbib laws of 

Combination. 150 

. Table of Elementary Bodies 152 

Laws of Combination 153 

Chemical Nomenclature and 
Symbols 155 

Combination by Volume 161 

Specific Heat of Atoms 162 

Isomorphism and Dimorph- 
ism 162 

Chemical Affinity 164 

PART ni. 


Classification of Elements 160 

Oxygen 169 

Management of Gases 174 

Chlorine 176 

Compounds of Chlorine with 

Oxygen 180 

Bromine 183 

Iodine 184 

Fluorine 186 

Sulphur. 187 

Sulphurous Acid 190 

Sulphuric Acid 192 

Chlorids of Sulphur 187 

Selenium 198 

Tellurium ^ 199 

Nitrogen 199 

The Atmosphere 201 

Compounds of Oxygen and 

Nitrogen 203 

Nitric Acid M .... 204 

Protoxyd of Nitrogen 206 

Nitric Oxyd 208 

Phosphorus 210 

Compounds of Phosphorus 

with Oxygen 213 

Carbon..... 216 






Carbonic Acid. 220 

Carbonic Oxyd 223 

Bisulphuret of Carbon 224 

Cyanogen. 225 

Silicon 227 

Silica 228 

Fluorid of Silicon 229 

Boron .... 229 

Boraoio Acid — 230 

Hydrogen 231 

Water 236 

Eudiometry 239 

Action of Platinum with Hy- 
drogen and Oxygen 242 

Oxyhydrogen Blowpipe. 244 

History of Water 246 

Peroxyd of Hydrogen 249 

Hydracids 250 

Chlorohydrio Acid 251 

Bromohydrio Acid « 255 

Iodohydrio Acid 256 

Fluohydrio Acid 257 

Solphydrio Acid 258 

Compounds of Hydrogen with 

class HX 261 

Ammonia 262 

Phosphuretted Hydrogen 265 

Compounds of Hydrogen with 

the Carbon group 266 

Marsh Gas 267 

defiant Gas 268 

Combustion and Structure of 

Flame 272 

Safety Lamp 276 

Metallic Elbiixnts 

General Properties of Metals 278 

Metallic Veins. 278 

Physical Properties of Metals 280 
Chemical Relations of the 

Metals 283 

Salts 285 

Potassium 288 

Compounds of Potassium..... 291 

Potash 292 

Salts of Potash 295 

Sodium M 300 

Caustic Soda, Common Salt. 301 

Sulphate of Soda 302 

Carbonate of Soda 304 

Nitrateof Soda 305 


Phosphates of S% da 306 

Borax. 307 

Lithium 307 

Ammonium ~ 398 

Compounds of Ammonium... 309 

Barium 311 

Strontium - 313 

Calcium. 314 

Gypsum 316 

Carbonate of Lime 317 

Magnesium 319 

Sulphate of Magnesia 320 

Aluminum 321 

Alums M 322 

Silicates of Alumina 323 

Manufacture of Glass 323 

Pottery 327 

Glncinum, Yttrium, Zirco- 
nium, Thoria 328 

Manganese « 328 

Iron 330 

Reduction of. 334 

Chromium 336 

Nickel 339 

Cobalt 340 

Zinc * 341 

Cadmium 342 

Lead. 343 

Uranium —.. 345 

Copper 345 

Vanadium, Tungsten, Colum- 
bium, Titanium, and Mo- 
lybdenum 348 

Tin 349 

Bismuth 350 

Antimony 352 

Arsenic 354 

Detection of Arsenic in poi- 
soning 357 

Mercury 361 

Calomel 364 

Salts of Mercury 366 

Silver 366 

Cupellation 368 

Gold 371 

Palladium 372 

Platinum 373 

Iridium, Osmium 375 

Rhodium, Ruthenium 376 








Introduction 377 

Nature of Organic Bodies.... 377 
Laws of Chemical Trans- 
formations 370 

* Equivalent Substitution 380 

Substitutions by residues 384 

Sesqui-salts, Direct Union... 385 
On Combination by Volumes 386 
Density of Carbon Vapor..... 386 
On the Law of the Divisibility 

of Formulas 387 

On Isomerism 388 

On Chemical Homologues.... 389 
Temperature of Ebullition... 390 
Analysis or Organic Sub- 
stances 390 

Density of Vapors 395 

Water 396 

Ammonia. 397 

Carbonic Acid 400 

Sugar, Starch, and Allied 

Substances.... 401 

Cane, Grape Sugars 401 

Sugar of Milk, Mannite 402 

Products of the Decomposi- 
tion of the Sugars 403 

The Vinous Fermentation... 403 

Lactic Acid.. 405 

Gum , ~ 407 

Starch 407 

Woody Fibre 409 

Xyloidine, Pyroxyline, Gun- 
cotton 411 

Transformation of Woody 

Fibre 412 

Destructive Distillation of 

Wood. 413 

Kreasote , 413 

Wood-tar, Paraffin, Coal-tar 414 

Petroleum..... 415 

Alcohols, Vinol 415 

Action of Acids upon Alcohol 417 

Ethers 419 

Nitric, Nitrous, Perchloric 

Ethers 420 

Sulphovinic Acid 420 

Silicic Ethers, defiant Gas... 425 
Products of the Ozydation of 
Alcohol 426 

Chloral, Sulphur Aldehyde... 428 

Acetic Acid 429 

Acetates, Acetate of Potash... 430 

Acetate of Lead 431 

Acetate of Copper, Chlorace- 

ticAcid 432 

Acetic Ether 433 

Mbthol 434 

Wood-spirit, Pyroxylio Spi- 
rit, Methylio Alcohol 434 

Sulphomethylio Acid. 435 

Oxydation of Methol 437 

Amylol, Amylio Alcohol 438 

Oxydation of Amylol 439 

Spermaceti, Wax.... 440 

Glycerids 441 

Soaps, Butyric Acid „. 442 

Phoeenine, Enanthylie and 

( Pelargonic Acids 443 

Oleine, Palmatine, Marga- 
rine, Stearine 444 

Fatty Acids 446 

Alkaloids of Alcohol Series 448 
Ethamine, Methamine, Amy- 

lamine .... 449 

Triethamine 450 

Bitter-Almond Oil 452 

Benzoilol 452 

Chlorinized Benzoilol, Hy- 

drobenxamide 453 

Benzoic Acid 454 

Benzen 455 

Salicylol 458 

Other Essential Oils 459 

Oil of Cinnamon 459 

Oil of Turpentine..... 459 

Oils of Juniper, Pepper, Ca- 
raway, Parsley, Ac 460 

Camphor, Borneo Camphor... 461 

Resins 462 

Caoutchouc, Gum-Elastic... 462 
Gutta Percha 463 

Vegetal Acids 463 

Oxalic Acid 464 

Tartaric Acid 465 

Racemic Acid, Malic Acid.... 467 

Citric Acid 469 

Tannic Acid, Tannin 469 

Gallic Acid M 470 





Vegetal Alkaloids 471 

Alkaloids of Cinchona 472 

Alkaloids of Opium 473 

Morphine, Codeine, Naroo- 

tine M 474 

Strychnine, Bruoine, Pipe- 

riue 475 

Theine, Caffeine, Theobro- 
mine, Solanine 476 

Veratrine, Aconitine, Sangui- 
narine, Emetine, Nico- 
tine, Conine 477 

Amygdaline, Emulsine - 478 

Salicine, Saligenine, Salire- 

tine, Helioine 479 

Populine, Phloridxine 480 

Coloring Matters. 481 

Leeanorine « 481 

Orcine, Evernio Acid, Litmus 482 
Xanthine, Alizarine, Madder 

lake „ 483 

Carthamine, Hematoxyline. 483 
Quercitrine, Luteoline, Mo- 

rine, Chlorophyll 483 

Indko 484 

Sulphindigotic and Sulpho- 
purpuric Acids, Saxon 

Blue 485 

Isatine, Anthranilio Acid..... 485 

The Cyanic Compounds 486 

Hydrocyanic Acid 486 

Cyanid of Potassium 488 

Cyanid of Ammonium. 488 

Cyanogen 488 

Cyanates 480 

Urea 490 

Sulphooyanates - 491 

Sulphocyanio Acid 491 

Cyanoxsulphid, Mellon 492 

Polycyanids 492 

Perchloric Trioyanid, Per- 
chlorio Dicyanid, Cya- 

nuric Acid 493 

Melamine, Ammelid, Amme- 

line 494 

Fulminates 494 

Cyanethine 495 

Alanine, Vinic Urea 496 

Allophanio Acid... „ 496 

Trigenio Acid 497 

Cyaniline, Melaniline, Cy- 
ameline, Cyanbarma- 
line 497 


Ferroeyanids „. 498 

Yellow Prussiate of Potash... 499 
Ferrocyanic Acid, Prussian 

Blue 500 

Ferricyanid8, Bed Prussiate 

of Potash 500 

Nitroprussids 501 

Cobalticyanids 502 

Platinooyanids, Argentooya- 

nid of Potassium 503 

Aeids of the Urine and Bile.. 503 

Hippuric Acid, GlycolL 504 

Uric, or Lithic Acid. 505 

Allantoin, Alloxan. 506 

Alloxantine, Dialurio Acid... 507 

Uramile, Murexid. 508 

Parabanic Acid, Amalio Acid. 509 

Cholio, Cholalic Acids 509 

Choloidic Acid, Taurine, Hy o- 

cholalicAcid 510 

Biliary Calculi 510 

Nutbitivi Substances con- 

tainino Nitrogen 511 

Protein, Fibrin, Albumin, Ca- 
sein 511 

Gluten, Vegetable Albumin.. 512 

Legumin 512 

Leuoin, Tyrosin 514 

Yeast..'. 516 

Gelatin 517 

The Blood 518 

Blood Globules 518 

Hematosine 519 

Seroline 520 

Flesh Fluid 522 

Creatine, Creatinine 522 

SarcOsine, Inosinic Acid 523 

Saliva, Pancreatic Juice 523 

Gastric Juice. 524 

Pepsin, Bile 524 

Chyle, Urine 525 

Microcosmio Salt 526 

Milk 527 

Eggs 528 

The Brain and Nervous Sub- 
stance 528 

Bones 529 

Nutrition op Plants and op 

Animals 530 

Food of Plants 531 

Manures ; 532 

Digestion 534 

Respiration 535 

Vital Heat 537 

Appendix 539 

Digitized by VjOOQ IC 

Digitized by VjOOQ iC 





1. Our knowledge of nature begins with experience. 
While this teaches us that like causes, under similar cir. 
cumstances, produce like effects, we recognise also, as insepa- 
rable from our experience, the great principle that every event 
must have a cause. Man, " as the priest and interpreter of 
nature," seeks to extend his experience by experiment. 
Every experiment is but a question addressed to nature, ask- 
ing for an increase of knowledge; and if we question her 
aright, we may be sure of a satisfactory answer. 

2. Observation instructs us in a knowledge of the external 
forms of nature, and we thus acquire our first impressions of 
the various departments of Natural History. Our knowledge 
would, however, be very limited, without a constant effort 
to extend our experience by experiment. The nations of 
antiquity excelled greatly in many branches of human know- 
ledge, and their skill in the arts of design remains unequalled. 
Their ignorance, however, of natural phenomena, and the 
(aws by which they are governed, was remarkable; because 
they overlooked the true connection between cause and effect. 

1. What if the beginning of our knowledge of nature? What great 
principle do we recognise in connection with experience ? What is an 
experiment ? 2. What does obserration teach ? How does it extend out 



The ancient philosophy abounded in plausible arguments 
regarding those natural phenomena which could not fail to 
arrest the attention of an intelligent people ; but its reason- 
ings were based on an d priori assumption of a cause, and 
not upon an inductive inquiry after facts and their connec- 
tions. It failed to apply iteelf to the careful collection and 
study of facts in order to science. Facts in nature are th& 
expression of the Divine will in the government of the phy- 
sical world. The universe of matter is made up of nets, 
which, observed,, traced out, and arranged, lead us to the 
knowledge of certain laws and forces which proceed directly 
from the mind of God. These are the " laws of nature : 
science is but the exposition of them and of science based 
upon such grounds, the ancient philosophy was completely 

3. It is important to distinguish that knowledge which is 
purely intellectual in its character, from that which results 
from observation and experience. Speaking of this subject, 
one of the most learned of living philosophers remarks : "A 
clever man, shut up alone, and allowed unlimited time, might 
reason out for himself all the truths of mathematics, by pro- 
ceeding from those simple notions of space and number, of 
which he cannot divest himself without ceasing to think ; but 
he could never tell, by any effort of reasoning, what would 
become of a lump of sugar if immersed in water, or what 
impression would be produced on the eye by mixing the 
colors yellow and blue." — (Eerschel.) We may, however, 
with propriety doubt, whether there is any knowledge or 
philosophy so purely intellectual, or absolute, that it does 
not imply some previous recognition of physical facts. 

4. The observation of facts forms only the foundation of 
science, — an isolated fact has no scientific value. The know- 
ledge of physical laws deduced from the study of observed 
facts will enable the philosopher to foretell the result of the 
possible combination of those laws, and to assign reasons for 
apparent departures from them. In this way discoveries are 
predicted and detailed ; observation is anticipated, and called 

Characterize the ancient philosophy. How did it fail? What art 
facts ? What are laws of nature ? What is science ? 3. What convenient 
distinction is named? What remark is quoted in illustration of this? 
4. What is said of observation? What of an isolated fact? What 
does a knowledge of natural laws enable the philosopher to do? 




on to verify tbe alleged discovery. The perturbations of the 
planet Uranus indicated the existence of some body in space 
heretofore unknown. When Le Verrier had reconciled these 
disturbances with the supposed influence of a new planet, 
and determined its elements of motion, he had as truly dis- 
covered the remote, sphere, as when the German astronomer! 
by pointing his telescope to the precise place in the heavens 
which Le verrier had designated, announced to the world 
that the stupendous prediction was verified by observation. 
In like manner, a familiarity with chemical laws enables the 
chemist to foretell the result of combinations which he has 
never investigated, and in some cases to assign with confi- 
dence the constitution of bodies which he has never ana- 

5. Our knowledge of Natural Science is conveniently 
classified under the three great divisions of Natural History, 
Physical Philosophy, and Chemistry. The first teaches us 
the characters and arrangement of the various forms of ani- 
mal and vegetable life and minerals, giving origin to the 
sciences of Zoology, Botany, and Mineralogy. Physical 
Philosophy explains the forces by which masses of matter 
are governed, and unfolds the laws of Light, of Electricity, 
and of Heat. 

Chemistry teaches us the intimate and invisible constitu- 
tion of bodies, and makes known the compounds which may 
be formed by the union of simple substances, the laws 
of their combination, and the properties of the new com- 
pounds. It investigates the forces resident in matter, and 
which are inseparable from our idea of molecular action, — 
forces whose play produces the phenomena of Light, of 
Heat, and of Electricity. Chemistry also unfolds the won- 
derful operations of animal and vegetable life, so far as their 
functions depend upon chemical laws, as in die processes of 
respiration and digestion, giving the special department of 
Physiological Chemistry. 

Illustrate this in case of the perturbations of Uranus. 5. How is out 
knowledge of nature classified? What does the first teach? Physical 
philosophy teaches what? Define the province of Chemistry. 




General Properties of Matter. 

6. Experience, founded on the evidence of our senses, con- 
vinces us of the existence of matter. We feel the resistance 
which it offers to our touch ; we see that it has form, and 
occupies space, and hence we say it has extent ; and, lastly, 
we attempt to raise it, and we find ourselves opposed by a 
certain force which we call weight. 

Matter possesses extension, because it occupies some space. 
It is impenetrable, because ono particle of matter cannot 
occupy the same space with another at the same time. It 
has gravity, because it obeys the law of universal attraction. 
Whatever, therefore, possesses these three qualities, is 

7. All the changes of which matter is capable may be 
referred to one of three great principles or forces, and to 
their modifications or combinations. These are Attraction, 
Bepulsion, and Vitality. 

Attraction is divided into Mechanical and Chemical. 

8. Mechanical Attraction is divided into, I. Gravitation, 
acting at all distances, and between all masses. 2. Cohesion, 
acting between bodies or particles of the same kind only, 
and at immeasurably small distances. To this power are 
referred all the phenomena of solidification and crystalliza- 
tion. 3. Adhesion, acting between bodies of unlike kinds, 
at immeasurably small distances, and forming mixed masses. 
Chemical Attraction, or Affinity, exists only between mole- 
cules or particles of unlike kinds, acts only at immeasurably 
small distances, and produces homogeneous masses which 
have properties unlike the constituent elements. In a word, 
gravity acts on all matter and at all distances. Cohesion 
acts only on the same kind of matter at inseosible distancos. 
Chemical affinity acts only between unlike particles at in- 
sensible distances. 

Repulsion is a force seen in the impenetrability of matte* 

6. Whence our knowledge of matter? Define its properties. 7. Name 
three forces governing matter. 8. Subdivide mechanical attraction. 
How is chemical distinguished from mechanical attraction? What of 
repulsion ? Define vitality. 




and in its power of expansion. It is the antagonist of co- 
hesion, or, as it is sometimes called, the attraction of aggrega- 
tion. Heat resolves the several forms of mechanical attrac- 
tion, and surrenders matter to the dominion of repulsive force, 
by which its particles or molecules are widely separated. 

Vitality rules superior to all the laws of mechanical and 
of chemical attraction, suspending, modifying, or applying 
them for the production of those complicated results which 
are seen in the organized structures of plants and animals. 

9. Such are the great forces to which matter is subject 
All the changes resulting from the operation of the forms 
of mechanical attraction belong to Physics. Those referable 
to vitality fall within the province of the physiologist. 

The consideration of the changes produced in matter by 
the exertion of affinity, or chemical attraction, constitutes 
the appropriate business of the chemist. 

All that relates therefore to physics might be properly 
dismissed from a manual of chemistry ; but it is usual for 
the chemical student to devote a share of his attention to 
those departments of physics, some knowledge of which is> 
essential to a correct understanding of chemical phenomena." - 

Of Mechanical Attraction. 

10. Gravitation is a force measured in any particular case 
by weight, whether we speak of a movable mass capablo of 
equipoise in our balances or of the weight of the planets as 
deduced from their observed motions. It acts at all dis- 
tances upon all matter, and is directly as the mass and in- 
versely as the square of the distance. The weight of a body 
is therefore proportioned to the number of molecules or par- 
ticles which it contains. 

11. Cohesion, is seen alike in solids, in fluids, and in 
gases — three states of matter incident to the equilibrium of 
the forces of repulsion and cohesion, and modified by the 
laws of heat. Those who regard light, heat, electricity, and 
magnetism as imponderable bodies, refer their properties 
also to the antagonistic power of repulsion, by which these 
manifestations are so controlled that we have no proof of 
the existence of mutual cohesion among their particles. 

9. What does physics include? 10. How is Gravitation measured t 
Define its law. 11. What of Cohesion ? 




In the force of cohesion, or attraction of aggregation, at 
manifest in solid bodies! we recognise a power which opposes 
the division of matter. 

12. Divisibility of matter. — The question of the infinite 
divisibility of matter has in past times been the subject of 
most animated discussions, and until the discoveries of modern 
chemistry, no satisfactory solution was reached. We know 
that the largest and most solid masses of matter, even en- 
tire mountains, may be ground down by mechanical force to 
dust so fine that the winds will bear it away, but each mi- 
nute particle still occupies some space; and we may imagine 
that a great multitude of smaller particles may be formed 
from its further division. A grain of gold may be spread 
out so thin as to cover 600 square inches of surface on silver 
wire, and one ounce, in this manner, be made to cover 1300 
miles of such wire. One grain of green vitriol, (sulphate 
of iron,) dissolved and diffused in 20 million grains of water, 
will still be easily detected by the proper tests. The delicate 
perfume of musk and the aroma of flowers are remarkable 
examples of minute division in matter. 

The organic world also presents us with beautiful ex- 
amples of the great divisibility of matter, in the remarkable 
forms of animalcules revealed by the microscope, many 
millions of which can be embraced in a single drop of water. 
Tet each of these inconceivably minute organisms has its 
own muscular, digestive, and circulatory systems. How mi- 
nute, then, the ultimate particles, of which many myriads 
must be contained in each animalcule I 

Chemistry has happily resolved the question of infinite 
divisibility, by proving that all matter oonsists of certain 
particles of definite values, whose relative weights and bulks 
may be precisely determined. These particles are called — 

13. Molecules,* or Atoms. — Ultimate chemical analysis 
has demonstrated that matter consists of many distinct 
varieties, called elementary or simple bodies, and that 

12. What degree of divisibility exists in matter? Give some illustra- 
tions. 13. What is said of molecules? 

* Molecule, a diminutive of mole*, a mass. This term is preferable to 
'atom* or 'ultimate particle/ as implying no theory, which both the others 
do. Atom is from a, privative, and temno, I cut, signifying their supposed 




these several separate sorts of matter possess each its 
own combining quantity, from which it never varies, and 
this quantity, called its equivalent, atomic, proportional, or 
combining number, is susceptible of accurate determination 
by the balance. The molecules of simple bodies are neces- 
sarily simple themselves, while the molecules of compound 
bodies are, on the contrary, complex. Whatever size these 
molecules may possess, they are the centres of all the 
forces and qualities whose united effects and activity give 
matter its physical or chemical properties. Although we 
may never know the absolute weight of any molecule, we do 
know with much certainty the relative size and weight of 
the molecules of over sixty sorts of simple matter, which che- 
mistry has revealed to us. The laws of crystallogeny also 
inform us that these molecules have an inherent difference 
of form ; some being spherical, while others are ellipsoidal. 

Of Cohesion in reference to the three states of Matter, 
the Solid, the Liquid, and the Gaseous. 

14. Properties of Solids. — It is a distinguishing pro- 
perty of solids to have their particles bound together by so 
Btrong an attraction as in a great measure to destroy their 
power of moving among each other. 

No solid, however, not even gold and platinum, which 
are the most compact solids known, has its particles of mat- 
ter so aggregated as to be incapable of some condensation. 
Blows, pressure, or a reduction of temperature, will condense 
almost all solids into a smaller bulk. Water may even be 
forced through the pores of gold, by very great mechanical 
pressure. All solid bodies are, therefore, considered as por- 
ous, and their particles are believed to touch each other in 
comparatively few points. 

Cohesion in solids may be destroyed either by mechanical 
violence, as in pulverization ; by solution, as in the case of 
saline bodies soluble in water ; or by the agency of heat, as 
in the fusion of wax or lead. The mobility of the particles 
in solid bodies is shown also in the elasticity, malleability, 
ductility, and laminability of many metals, which are among 
their most useful properties. Hardness is a quality having 

What forms hare the molecules ? 14. What mobility hare particles in 
solids ? What of pores in solids ? How may cohesion be destroyed ? \ 





no relation to the preceding, and is possessed by solids in very 
various degrees, and apparently without reference either 
to the density or chemical nature of the substances, — for 
gold and platinum, among the heaviest of known bodies, are 
comparatively soft, while the diamond, which is only about 
one-sixth part as heavy as these metals, is the hardest of all 
known substances. Cohesive attraction, when once disturbed 
by mechanical violence, is not usually brought into exercise 
again by mere approach of the separated particles. The 
broken fragments of a glass vessel or portion of stone do not 
reunite at ordinary temperatures. Nevertheless! we have 
some examples of a contrary nature. 

If we press together 
two smooth surfaces of 
lead, clean and bright, 
as, for example, the 
halves of a leaden 
sphere, (fig. 1,) cut 
through, they will ad- 
here or unite together 
so firmly as to require 
the power of several 
pounds weight to draw 
them asunder, as shown 
in the annexed figure. 
The plates of polished 
glass, also, which are 
prepared for large mir- 
rors, if allowed to rest 
together with their sur- 
faces in close contact, 
have been known to 
unite so firmly as to 
break before they would yield to any effort to separate them. 
In these cases, actual contact of contiguous particles is ef- 
fected, and thus the conditions of cohesive attraction are 
fulfilled. We may regard the welding of iron and the cohe- 
sion of masses of dough or putty as examples of a similar 
kind. The casting of metals by voltaic electricity, from cold 
solutions of their salts, also affords us elegant examples of 
adhesive attraction. 

What of hardness ? Gire examples of cohesion at common temperatures. 





15. In fluids, the particles have perfect freedom of mo- 
tion among themselves. They are either inelastic liquids, 
like water, or elastic gases or vapours, like air and steam. 
A gas is a permanent elastic fluid : a vapour is such only io 
certain conditions of temperature and pres- 
sure. In water we have a familar example of 
a body, presenting the three conditions of mat- 
ter, in the ordinary changes of the seasons. 

Liquids are not completely inelastic, but 
are compressible to a very slight extent by 
pressure, as is shown in the apparatus of 
Oersted, fig. 2. A small glass bulb b, with 
a narrow neck, is filled with water lately 
boiled, and placed in the glass vessel a, also 
filled with water by the funnel g; a metallic 
plug h is forced down by the screw k, pro- 
ducing any required pressure. A small glo- 
bule of mercury in the stem of b by its de- 
scent notes the amount of condensation which 
the water in b suffers. No change of dimen- 
sions in the glass b can happen, because it is 
equally compressed from within and without. 
In this way the compressibility of water has 
been shown to be equal to one part in 22,000 
for each atmosphere of 15 pounds pressure. 
Alcohol has about half this degree of compres- 
sibility; ether about one-third more, and 
mercury only about one-twentieth as much. 

16. CapUlary attraction is a form of cohesion seen in 
liquids. If a tube with a very fine bore, and open at both 
ends, is immersed in water, it will be observed that the 
liquid rises, as seen in fig. 3, to a certain 
elevation in the tube, and to a less degree 
also on the outer surface. In mercury, (fig. 
4,) on the contrary, which does not moisten 
the glass, there is a depression of the column 
in the tube, and the surfaces of the mercury 
are- convex. The height to which a fluid Fig. 3. Fig. 4. 
will rise in a tube by capillarity is inversely as the diameter 

Pig. 2. 

15. How are the particles in fluids? Are fluids elastic? Illustrate it 
by the case of water? 16. What is capillarity? What relation has dia- 
meter to capillarity? 





Fig. 6. 

of the tube. Two plates of glass held as in fig. 5, opening 
like the leaves of a book, and their lowet 
edges immersed in a fluid, show this law 
by the curve which the liquid assumes. 
By the power of capillary attraction, the 
wick supplies fuel to the lamp or candle. 
Plugs of dry wood driven into holes bored 
in granite, and then saturated with water, 
swell so much by the water taken into their 
I pores by capillarity that the rocks are split 
open. Even a bar of lead or tin, bent like the 
letter U and placed by one end in a vessel 
of mercury, will, after some time, convey it out of the vessel 
drop by drop. Two small balls, one of wax and one of cork, 
(fig. 6,) thrown upon the surface of 
water, manifest repulsion at first, 
> for the water not wetting the wax 
while it does the cork, causes an 
elevation about the latter, from 
which the former, so to speak, rolls off, and the balls sepa- 
rate in the direction of the arrows. Two balls of cork, for s 
like reason, attract one another. Hence the familiar fact 
that chips on the surface of quiet water always crowd to- 
gether, and gather about a log or larger body on the surface. 
The wetting of surfaces by a fluid is perhaps a sort of chemi- 
cal affinity. Iron, glass, the skin, or a piece of wood are 
not wet by mercury; while gold, silver, lead, and many 
other metals are so. Oil spreads itself in a thin film on the 
surface of water, and by its cohesion quiets the agitation of 
moderate waves. 

17. The cohesion in liquids is much greater than is com- 
monly imagined. A disc of glass suspended from the 
beam of a balance over a surface of water will adhere with 
a measurable force to the water when brought 
in contact with it. The force required to with- 
| draw it is that which will rupture the cohe- 
! sion of the outer row of particles at the edge of 
the disc, then the next row, and so on to the 
centre a, as shown in the circles on fig. 7. In 
Fig. 7. the soap-bubble we see a thin film of water, 

Illustrate this by fig. 6. Explain the action of light bodies on water. 
What is wettiug? 17. What of cohesion in liquids? Explain the adhe- 
sive disc and the soap-bubble. 

Digitized by VjOOQ IC 



f lying us a beautiful example of the cohesive power of water, 
t is a great hollow drop of water. The cohesive power 
in the film of the bubble is so great that if the pipe bo 
taken from the mouth before the bubble leaves it, a stream 
of air will be forcibly driven from the bore by the contrac- 
tion of the film, which will deflect the flame of a candle. To 
the same cause is ascribed the spherical form of the dew- 
drop, the cohesion in the outer row of particles. 

18. In the structure of plants and of animals, capillary 
attraction performs functions of the highest importance in 
the economy of life. Animal membranes possess the power 
of exuding or of absorbing fluids from their surfaces. This 
power has by several authors been considered as a special 
attribute of animal tissues, and as such has received the 
name of endosmose and exosmose, or the inward and the out- 
ward force of membranes. These actions are generally 
regarded as modifications of capillarity, and may be well 
illustrated by the endosmometer, (fig. 8.) An 
open glass b has it lower end tied over by a bit 
of bladder c, and its upper opening elongated 
by a narrow glass tube a, this apparatus is 
filled with weak sugar-water, and is placed in 
an outer vessel n, filled with strong syrup of 
sugar. Soon the column of fluid is seen to 
mount from a to o or out at the top, from the 
penetration of the denser fluid through the 
membrane. The power which plants possess of 
absorbing the nutritive fluids from the soil 
through the delicate bulbous ends of their spog- 
nioles is supposed to be identical with that force Fig. 8. 
shown in this instrument. 

19. In gases, the force of cohesion among the particles 
is entirely subordinate to the repulsive action by which they 
are expanded. The physical properties of gaseous bodies 
are best understood when we study 

The Mechanical Properties of the Atmosphere. 

20. We on the surface of this earth are at the bottom 
of a vast aerial ocean, in which we live and move and have 

Whence the form of the dew-drop ? 18. What i§ endosmoso ? What 
exosmose? Explain the endosmometer. 19. What of cohesion in gases ? 





our being. From its chemical influence we cannot escape, 
nor free ourselves from the vast load of its mechanical pres- 
sure which we unconsciously sustain. It penetrates deeply 
into the crust of the earth, and is largely dissolved in its 
waters. All that relates to its chemical history will be 
given in its appropriate place. Its mechanical properties 
demand attention now. What is true of the mechanical 
properties of air is also true of the gases. 

21. Elasticity. — Vessels filled only with air we call 
empty ; but it is obvious, when we plunge an empty air-jar 
beneath the surface of water, that it contains an elastic and 
resisting medium, which must be displaced before the vessel 
can be filled with water. Elasticity is the most remarkable 
physical property of the atmosphere and of all gases. Upon 
this property depends the construction of 

22. The air-pump , an instrument in principle like the 
common water-pump. It depends for its action on the elas- 
ticity of the air. Suppose. two tight-bottomed cylinders, a 
and b, ("fig. 9,) to be filled with air. If a solid plug, or pis- 
ton, is fitted to each so tightly that no air can pass between 

it and the sides of the vessel, we 
shall find it impossible to force down 
the piston to the bottom of the cylin- 
der. It descends a certain distance 

q with an increasing resistance, and 
is again restored, as with the force of 
a spring, so soon as the pressure is 
removed. If we suppose one of the 
pistons to be in the position shown in 
by and the air beneath it of the same 
tension or. density as that above, and 
we attempt to draw out the plug by 
its stem, we also feel a continually 
increasing resistance, and the piston 
returns forcibly to its former posi- 

our hold. We thus demonstrate the 



> ■ 



it! 1 '" 

1 Mi 





Fig. 9. 
tion when we release 

elasticity of the air, and also its weight and pressure, 
an arrangement of apparatus, slightly modified, is an air- 
pump. If each of the pistons is pierced with a hole, over 

20. What is said of the aerial ocean? 21. Demonstrate the elasticity of 
air by an empty vessel. 21. What is the air-pump ? How does it em 
ploy elasticity ? Illustrate this by fig. 9. 





which is. a flap, or valve, of leather or silk v, opening upward, 

and closing with the slightest downward pressure, and a 

similar opening, or valve, 

be provided in the bottom 

of each cylinder v, we have 

an air-pump. (Fig. 10.) ~ 

It remains only to connect 1 

the cylinders by a duct 

with the plate on which 

the air-receiver R is placed, 

and to provide suitable 

movements for the pistons 

by a lever or otherwise, | 

and our instrument is 

complete. The plate and L " 

receiver are accurately 

ground to fit air-tight, and 

great pains are taken to 

have all parts of the ap- Fi s- 10 » 

paratus as perfectly air-tight as possible. 

23. Vacuum. — It is obvious that the air in the receiver will, 
by virtue of its elasticity, rush into the cylinders alternately 
as these are moved ; the valves in the cylinders preventing 
the return of the air to the receiver, while they permit the 
escape of the successive portions from within, and those on 
the piston closing the access of the outer air. Thus, with 
each movement of the lever, fresh portions of air from the 
receiver, more and more rare each time, will find their way to 
the cylinders and be pumped out, while the space in R be- 
comes constantly more void, until the vacuum is completed. 
This happens whenever the weight and resistance of the 
valves in the cylinders is greater than the elastic force of the 
rarefied air in the receiver. And hence it is obviously impos- 
sible to make a perfect vacuum by mechanical means. There 
will always remain a certain very tenuous atmosphere in 
even the most perfect and delicate air-pump, unless, indeed, 
it be removed by chemical means. This may be done by em- 
ploying a bell-jar filled with carbonic acid, the last portions 
of which may be removed by potassa or caustic lime — prc- 

How are the valves of the pump arranged? 23. What is a vacuum? 
Why is a perfect vacuum impossible ? How max the last portions of air 
be removed ? 






viously placed for that purpose in a vessel on the pump- 
plate. The French instruments often have the cylinders of 
glass, to expose the mechanical movements 
of the valves and pistons. Excellent air- 
pumps, with only one cylinder, on the plan 
proposed by Leslie, are furnished by the in- 
strument-makers in Boston and New York. 
24. The bulk and density of the atmosphere 
varies with the mechanical pressure to which 
it is submitted. This inference is drawn 
from what has just been said regarding the 
theory of the air-pump. The volume of the 
air is inversely as the pressure to which it 
is subjected, while its density is directly as 
this pressure. This is known as Mariotte's 
law, from its discoverer, an Italian philoso- 
pher of that name. 

Fig. 11 shows the simple apparatus used 
for demonstrating this law. It is a glass tube 
turned up and sealed at the lower end : a gra- 
duated scale of equal parts is attached to it. 
Mercury is poured into the open end of this 
tube so as to rise just to the first horizontal 
line ; a portion of air of the ordinary elas- 
ticity is thus enclosed in the short limb of 
9 inches. Now if mercury be poured into 
the longer leg, so that it may stand at 30 
inches above the level of the mercury is 
the shorter leg, it will press with its whole 
weight on the included air, which will then 
be found to occupy 4} inches, or only half 
of its former space. If, in like manner, the 
column of mercury be increased to twice this 
length, its pressure on the included air will 
n be tripled, and the space occupied by it will 
| be reduced to one-third, and so on in simple 
jf proportion. It consequently happens that 
' at a pressure of seven hundred and seventy 
Fig. n. atmospheres, air would become as dense as 

24. What if the relation of volume to density in the air? What is the 
law of Mariotte ? Explain figure 11. When is air as dense as water ? 





vatcr. The terms tension and density, as applied to gases, 
uave the same meaning. 

25. The weight of the atmosphere is of course shown bj 
<he air-pump. The receiver is fixed by the first stroke of 
the pump, and if we employ on the plate a small glass, 
>pen at both ends, (fig. 12,) and cover the 
upper end with the hand, we shall find it 
fixed with a powerful pressure. This is 
vulgarly called suction, but is plainly due 
>nly to the weight of air resting on the sur- 
face of the hand, and rendered sensible 
by the partial withdrawal of the air be- 
low. Hence, all vessels of glass used on K fr **• 

the air-pump are made strong, and of an arched form, to 
resist this pressure. Square vessels of thin glass are imme- 
diately crushed on submitting them to the at- 
mospheric pressure, or exploded by the removal' 
of the surrounding air while they are sealed. The 
weight of the air is also well shown by the burst- 
ing of a piece of bladder-skin tied tightly over 
the mouth of an open jar on the plate of the 
air-pump. As the pump is worked, the flat sur- 
face of the bladder becomes more 
and more concave, and at length 
bursts inward with a smart ex- 

26. Numerous common facts and 
experiments illustrate the same 
thing. Were the atmospheric pres- 
sure removed from under our feet, 
we should be unable to move ; and 
the difficulty we experience when 
walking on clay is due to a partial j 
vacuum formed by the close con- 
tact of the foot to the plastic soil, 
excluding the air. Boys raise . 
bricks and stones by a " sucker" 
of moist leather, on the same prin- 
ciple. The power of the atmo- 
spheric pressure to raise heavy weights is well shown in the 

Fig. 13. 

25. What illustrations of the weight of the air are given in figs. 12 and 
13 ? 26. How is the weight raised in fig. 14 ? 




annexed apparatus, (fig. 14.) A glass jar, having an open 
bottom, is covered with impervious caoutchouc. When a 
vacuum is produced in the jar, the yielding cover rises, 
carrying with it a weight which is below. This is sustained 
in the air, as by an elastic spring. The amount of the atmo- 
spheric pressure has been experimentally determined as equal 
to fifteen pounds on every square inch of surface. This fact 
is demonstrated by the 

27. Barometer. — This instrument (as its name implies) 
enables us to weigh the air. It was discovered by Torricelli, 
an Italian philosopher, in the year 1643. When a 
glass tube, (fig. 15,) sealed at one end, and about 36 
inches long, is filled with mercury, the open end closed 
by the finger, and inverted in a vessel containing mer- 
cury, so that the open end may be beneath the sur- 
face, so soon as the finger is withdrawn the mer- 
curial column is seen to fall some distance, and, 
after several oscillations, to come to rest at a cer- 
tain point, where it is apparently stationary. At 
the level of the sea, this point is found to be about 
30 inches above the surface of the mercury in the 
basin. The empty space above the mercury is the 
most perfect vacuum that can be produced; and, 
in honor of its discoverer, is called the Torricellian 

The mercury is sustained at this height by the 

pressure of the atmosphere on the surface of the 

fluid in the basin, and the height of the column 

varies with the atmospheric pressure, and with toe 

elevation of the instrument above the level of the 

ocean. Had water been the fluid employed, it would 

have required a tube more than 34 feet long to 

accommodate the column. If the experiment be 

tried above the ocean level, as on the top of a lofty 

mountain, the column of mercury will be found of 

I a less elevation in proportion to the height of the 

[mountain. It was the distinguished Pascal who 

* first, in 1647, suggested this experiment on the top 

Fig. 15. of a mountain in France, as conclusive proof that 

27. What is the barometer ? Describe its principle ? What is the To- 
ricellian vacuum? Why is 30 inches the height? What was Pascal's 
suggestion ? 





it was the weight of the air which sustained the mercury in 
the barometer. 

28. The principle of the barometer is beautifully shown in 
16. A large bell-glass, with a wide mouth c, has two sy- 
phon barometer tubes attached. One a has the mercury stand- 
ing at the proper height at a, while its cistern enters the bell. 
The other tube at one end also enters the bell, but, bending 
upon itself, it holds a portion of mercury in the outer cis- 
tern b on its other extremity. When this apparatus is 
placed on the air-pump and exhausted of air, the 
mercury a falls in proportion to the vacuum pro- 
duced, while that in b mounts in like proportion. 
In a we see the effect of diminished pressure, as 
on a mountain or in a balloon ; in b the pressure 
of the external air causes the mercury in it to 
mount, forming a gauge of the exhaustion. 

29. If the tube of the barometer has an area 
of one inch, and the height of the column is 30 
inches, the weight of the mercury sustained in it 
is by experiment found to be fifteen pounds. And 
this is the pressure which the atmosphere ex- 
ercises on every square inch of the earth's sur- 
face. A column of atmospheric air one inch 
square, and reaching to the uppermost limits of 
the aerial ocean, will also weigh, of course, just 
fifteen pounds. We thus come to regard the 
mercury in the barometer as the equipoise on one 
arm of a balance, of which the counterpart is 
the atmospheric column. As the latter varies { 
daily from meteoric causes, so also does the 
height of the mercurial column oscillate in just 
proportion. Hence the barometer is properly called a 
"weather-glass," and by its movements we judge of the 
approach of storms. These changes of level sometimes 
amount at the same place to 2 or 2 J inches, although 
usually they are much less. 

Various forms of the barometer are in use : those for 
measuring the elevation of mountains are so constructed 


Fig. 16. 

28. How is the principle of the barometer explained in fig. 16? Why 
does the mercury in a fall? Why does that in o rise? 29. What is 
the pressure of air on a square inch of surfaoe ? How is this shown by 
the barometer ? How is tho barometer a weather-glass ? 





as to be easily transported. A good 
form of the mountain barometer is 
shown in fig. 17, supported on a tri- 
pod, which, with the instrument, can 
be safely packed in a leather case. 

80. The Aneroid Barometer is de- 
signed to supersede the mercurial in- 
strument in those situations where the 
oscillating motion of the mercury de- 
stroys the value of its indications, as in 
travelling, in aeronautical excursions, at 
sea, and on many other occasions when 
the common barometer is inconve- 
nient. It depends on the variation 
in form of a thin vase D J) (fig. 18) 
of copper, which being partially ex- 
hausted of air changes its dimensions 
with every variation in atmospheric 
^pressure. These motions are multi- 
plied and transferred by the combina- 
tion of levers C, K, 1, 2, and 3, &o., 
in such a manner that the index 
reads the barometric conditions of 
the atmosphere on a dial. The in- 
dex is set by adjusting screws, to 
correspond with a standard mer- 
curial instrument, and the accuracy 
of each aneroid is tested by the air- 

81. Weight of the Atmosphere. — One hundred cubic inches 
of atmospheric air at 80 inches of the barometer and 60° Fahr. 
weigh 30 T ^/^ grains, while the same bulk of water would 
weigh about 25,250 grains. Air of the above condition is as- 
sumed as the standard unity for the density of all other aeri- 
form bodies. A man of ordinary size has a surface of about 
15 square feet, and he must consequently sustain a pressure 
on his body of over 15 tons. This prodigious load he bears 
about with him unconsciously, because the mobility of the 
particles of air causes it to bear with equal force on every 

Fig. 17. 

Fig. 18. 

30. What is the aneroid barometer? 81. What is the weight of air? 
What weight of air does a man sustain? 




part of his body, beneath his feet as well as on his head, 
and in the inner cavities as well as on the outer surface. 

32. Limit* of the AtmospJiere. — A person who has risen 
in a balloon, or on a mountain, to the height of 2*705 miles, 
or 14,282 feet, has passed through one-half of the entire 
weight of the air, and finds his barometer to indicate this bj 
standing at 15 inches. 

The air grows more and more rare as we ascend, and the 
barometer falls in exact proportion. The inconvenience 
which travellers have experienced in ascending high moun- 
tains has, it is said on good authority, been very much ex- 
aggerated. The heart continues its action under a diminished 
external pressure, and no serious consequences, it is believed, 
ever follow, as the bursting of bloodvessels or lesion of the 
lungs, as some have asserted. On the summit of Chimbo- 
razo, Baron von Humboldt found that his barometer had 
sunk to 13 inches 11 lines ; and the same philosopher de- 
scended into the sea in a diving-bell until the mercurial co- 
lumn rose to 45 inches : he consequently has safely expe- 
rienced a change of 31 inches of pressure in his own person. 

The upper limits of the atmosphere cannot be determined 
very accurately • but, from the refraction of light as observed 
in the rising and setting of stars, astronomers have inferred 
that it is probably about forty-five miles high. 

Weight and Specific Gravity, 

33. Weight is the measure of the force of gravity, and 
is directly proportional to the quantity of matter in a given 
space. Weight is determined by the balance, an instru- 
ment to which the chemist appeals at every step of his in- 
vestigations. Modern instruments enable us to determine 
this element of accurate science, to the greatest nicety. 

The specific gravity of a body is its weight as compared 
with an equal bulk of some other substance assumed as the 
unit of comparison. A cubic inch of gold is more than 19 
times as heavy as a cubio inch of ice or of water : hence the 
gold is said to have a specific gravity of 19, compared with 

Pure water has been adopted as the standard of compari- 

32. What is the height of the atmosphere? 33. What is weight? 
What is speeifio gravity I What is the standard of speciflo gravitj ? 





sou for the specific gravity of all solid and liquid substances, 
taken at 60° Fahrenheit. For gases and vapours, common 
air, dry and at the temperature of 60° and 30 inches of ba- 
rometric pressure, is the standard assumed. Regard is had 
to the conditions of temperature and pressure because the 
bulk of all bodies varies sensibly with these conditions. 

84. The specific gravity of solids is determined by the 
theorem of the renowned Archimedes, that " when a body 
is immersed in water, it loses a portion of its weight exactly 
equal to the weight of the water displaced." He thus de- 
tected the fraud of the goldsmith who fur- 
nished to King Hiero of Syracuse, as a crown 
of pure gold, one fashioned of base metal — the 
specific gravity of the debased alloy was too 
small for gold. It is plain that a solid dis- 
places, when immersed, exactly its own bulk 
of water, and loses weight to a corresponding 
amount. Hence, if we weigh a body first 
in air and then in water, the loss of weight ob- 
served, is equal to the volume of water, cor- 
responding to the bulk of the solid. Fig. 19 
shows a group of crystals of quartz suspended 
from the underside of the scale-pan by a fila- 
ment of silk. Its weight in air was previously 
determined. Its diminished weight in the 
water, subtracted from the weight in air, gives 
Fig. 19. a sum e q Ua i to the bulk of water displaced. 
From these elements is deduced the rule to find the specific 
gravity of a solid. " Subtract the weight in water from 

the weight in 
air, divide the 
weight in air 
by this dif- 
ference, and 
the quotient 
will be the 
specific gra- 
vity." Fig. 
20 shows the 
Fig. 20. balance ar- 

How is it determined ? What is the theorem of Archimedes ? 34. How 
is this illustrated in fig. 19 ? Give the rule for specific gravity 





ranged for taking the specific gravity of the solid a sus- 
pended in water from the hook b. A single example will 
serve to illustrate this rule. We find, on trial, that the 

Weight of a substance in air, is. 357*95 gra. 

Weight of the substance in water 239-41 " 

Difference 118*4 « 

847-95 A<l , a 

jj^ - 3-01 specific gravity. 

35. The specific gravity of sub- 
stances lighter than water may be 
determined by attaching them to a 
mass of lead or brass, of known 
weight and density. Subtances in 
small fragments or in powder are 
placed in a small bottle, fig. 21, 
holding, for example, a thousand 
grains of water. Those soluble in 
water are weighed in a fluid in which 
they are insoluble and whose den- 
sity is separately determined. In 
these cases a simple calculation re- 
fers the results to the known den- 
sity of pure water. 

36. The specific gravity of liquids may 
be ascertained in a small bottle holding 
a known weight of pure water. These 
bottles usually have a small perforation in 
the stopper, as seen in the figure 22, through 
which the excess of fluid gushes out, and 
may be removed by careful wiping. The 
weight of the bottle, dry and empty, is 
counterpoised by a weight kept for that 
purpose. Fig. 22. 

37. The Hydrometer is an instrument of great use in de- 
termining the specific gravity of liquids without a balance. 
It is simply a glass tube, fig. 23, with a bulb blown on one 
end of it, containing a few shot, to counterbalance the instru- 
ment ; and a paper scale of equal parts is sealed within the 

Pig. 2L 

Give an example. 35. How is specific gravity determined on bodies 
lighter than water? on powders? on soluble substanoes? 36. On fluids? 
27. What is the hydrometer ? Describe its use. 





Fig. 24. 

stem. This scale indicates the points to which the stem sinks 
when immersed in fluids of different de&- 
sities. The fluid, for convenience, is 
placed in a tube or narrow jar, (fig. 24): 
the more dense the liquid is, the less 
quantity will the hydrometer displace, 
while in a lighter fluid it will sink deeper. 
The zero point of the scale is always 
placed where the instrument will rest in 
pure water, after which the graduation 
is effected on a variety of arbitrary scales, 
all of which can, however, be referred to 
the true specific gravity by calculation, 
or by reference to a table such as may be 
• found at the close of this volume. Hy- 
drometers are also prepared with the true 
specific gravities marked upon them, read- 
ing even to the third decimal place accurately. The scales 
of these instruments read either up or down, according as the 
fluid to be measured is either heavier or lighter than water. 
In case of alcohol, the graduation of the hydrometer is made 
to indicate the number of parts of pure alcohol in a hundred 
parte of a liquids—absolute alcohol being 100, and water 0. 
The hydrometers of Baume* (French scale) are much used 
in the arts. These instruments are of the greatest service 
to the manufacturer, and, when carefully made, are suffi- 
ciently accurate for most purposes of the laboratory. They 
should always be proved by comparison with the balance 
and thermometer before they are accepted as standards. 
For many purposes they are made of brass or ivory, as well 
as of glass. 

Little balloons or bulbs of glass, are frequently 

employed to find, in a rough way, the density of 

fluids. When several of them are thrown in a 

fluid of known density, some will sink, some rise 

even with the surface, and others will just float. 

Those which just float are taken, and being 

Fig. 25. marked (as in fig. 25) with the density of the 

Jiquid which they represent, are then used to determine the 

specific gravity of liquids of unknown density. They are 

called specific gravity bulbs, and are of great service in as- 

What scales ore used in Hydroinoters ? What use is made of little 
bulbs of glass » 





certaining the density of gases reduced to a liquid by pres- 
sure in glass tubes, when, from the circumstances of the 
experiment, all the usual modes of ascertaining specific gra- 
vity are inapplicable. 

38. The water balloon, or " Cartesian devil," is an ele- 
gant illustration of the law of specific gravity. In this toy 
the balloon, or figure, contains a portion of water 
just sufficient to enable it to float. It is placed 
in a tall jar of water, over the top of which is tied 
a cover of India-rubber. Pressure upon this cover 
forces an additional quantity of water into the 
balloon by an opening (v 1 fig. 26). The density 
of the mass is thus increased, and it sinks until 
the pressure is removed, when, the air in the bal- 
loon expanding, forces out the superfluous water, 
and the glass rises again. Such is the mode pro- 
vided by nature in the structure of the nautilus 
and ammonite, by which means those curious ani- Fig. 26. 
mals are able, at will, to rise or sink in the ocean. 

39. Specific Gravity of Gases. — It remains only, under 
this head, to speak of the modes used for determining the 
specific gravity of gases and vapors. For this purpose a 

globe, (fig. 28,) or other conveniently formed glass 
vessel, holding a known quantity by measure, 
(usually 100 cubic inches,) is care- 
fully freed from air and mois- 
ture, by the air-pump or exhausting 
syringe. It is then filled with 
the gas or vapor in question, at 
60° Fahrenheit, and 30 inches of 
the barometer, (33,) and weighed. 
The weight of the apparatus filled 
with common air being previously 
known, the difference enables the 
experimenter to make a direct com- 
parison. Figure 27 shows an appa- 
ratus for this purpose ; the globe b 
Fig. 27. j s provided w ith a stopcock e, and fitted by a 
screw to the air- jar a. The jar is graduated so that the 
quantity of air or other gas entering may be known from 

38. What is the water balloon. What animal has the same principle ? 
Uow is air weighed ? 39, Describe figures 27 and 28. How do we find 
lbs speeifie gravity of gases ? 

Fig. 28. 




the rise of the water in a. It is thus found that 100 cu- 
bic inches of pure dry air weigh 30-829 grains, while the 
same quantity of hydrogen gas weighs only 2*14 grains, 
being about fourteen times lighter than air. To dry the air 
or gas it must be made to pass through a chlorid of calcium 
tube, or other drying apparatus, before entering the balloon. 

Nature of Crystallization and Forms of Crystals. 

40. Nature of Crystallization. — The forms of living na- 
ture, both animal and vegetable, are determined by the laws 
of vitality, and are generally bounded by curved lines and 
surfaces. Inorganic or lifeless matter is fashioned by a dif- 
ferent law. Geometrical forms, bounded by straight lines 
and plane surfaces, take the place in the mineral kingdom 
which the more complex results of the vital force occupy 
in the animal and vegetable world. The power which de- 
termines the forms of inorganic matter is called crystalliza- 
tion. A crystal is any inorganic solid, bounded by plane 
surfaces symmetrically arranged and possessing a homoge- 
neous structure. • 

Crystallization is, then, to the inorganic world, what the 
power of vitality is to the organic ; and viewed in this, its 
proper light, the science of crystallography rises from being 
only a branch of solid geometry to occupy an exalted philo- 
sophical position. 

The cohesive force in solids is only an exertion of crystal- 
line forces, and in this sense no difference can be established 
between solidification and crystallization. The forms of 
matter resulting from solidification may not always be re- 
gular, but the power which binds together the molecules is 
that of crystallization. 

41. Circumstances influencing Crystallization. — Solution 
is one of the most important conditions necessary to crystal- 
lization. Most salts and other bodies are more soluble in 
hot than in cold water. A saturated hot solution will 
usually deposit crystals on cooling. Common alum and 
Glauber's salts are examples of this. Solution by heat, or 

How much do we thus find the air to weigh ? 40. What is crystalliza- 
tion said to be ? What is the cohesive force ? 41. Name some circum- 
stances which influence crystallization. 





fusion, also allows of crystallization, as is seen in the crystal- 
line fracture of zinc and antimony. Sulphur crystallizes 
beautifully on cooling from fusion, and so do bismuth and 
some other substances. The slags of iron-furnaces and sco- 
riae of volcanic districts present numerous examples of mine- 
rals finely crystallized by fire. Numerous minerals havo 
been formed by heating together the constituents of which 
they are composed. Blows and long-continued vibration 
produce a change of molecular arrangement in masses of 
solid iron and other bodies, resulting often in the formation 
of broad crystalline plates. Rail-road axles are thus fre- 
quently rendered unsafe. In short, any change which can 
disturb the equilibrium of the particles, and permits any 
freedom of motion among them, favours the reaction of the 
polar or axial forces, (42,) and promotes crystallization. 

42. Polarity of Molecules. — The laws of crystallization 
show that the molecules have polarity. That is, these mole- 
cules have three imaginary axes passing through them, whose 
terminations, or poles, are the centre of the forces by which 
a series of similar particles are attracted to each other to 
form a regular solid. These molecules are either spheres 
(fig. 29) or ellipsoids, (fig. 31,) and the three axes (N S) 

Fig. 29. Fig. 30. Fig. 31. 

are, always, either the fundamental axes, or the diameters of 
these particles. In the sphere (fig. 29) these axes are always 
of equal length, and at right angles to each other, and the 
forms which can result from the aggregation of such spheri- 
cal particles can be only symmetrical solids, such as the 
cube and its allied forms. The cube drawn about the sphere 
(fig. 29) may be supposed to be made up of a great number 
of little spheres (fig. 30) whose similar poles unite N and 
S. In the ellipsoid (fig. 31) all the axes may vary in length, 

42. What do the laws of crystallization show? What are the aorta of 
molecules? What forms have the molecules of bodies? What forms c*d 
come from the spherical particles ? How may the structure of the cube 
be shown? How are the axes of the ellipsoid ? 





giving origin to a vast diversity of forms. Under the in- 
fluence of heat, the crystallogenic attraction loses its polarity 
and force, and the body becomes liquid or gaseous, and sub- 
ject to repulsive force. The return to a solid state can ocour 
again only when the attractions become polar or axial. 

43. Crystalline Forms. — The mineral kingdom presents as 
with the most splendid examples of crystals. In the labora- 
tory we can imitate the productions of nature, and in many 
cases produce beautiful forms from the crystallization of 
various salts, which have never been observed in nature. 
The learner who is ignorant of the simple laws of crystal- 
lography, sees in a cabinet of crystals an unending variety 
and complexity of forms, which at first would seem to baffle 
all attempts at system or simplicity. Numerous as the natu- 
ral forms of crystals are, however, they may be all reduced 
to six classes, comprising only thirteen or fourteen forms. 
From these all other crystalline solids, however varied, may 
be formed by certain simple laws. 

44. The first class of crystalline forms includes the cube, 
(fig. 32,) the octahedron, (fig. 33,) and the dodecahedron, 

(fig. 34.) The 
faces of the cube 
are equal squares. 
The eight solid 
angles are similar, 
and also the twelve 
Fig. 32. Fig. 33. Fig. 34. edges. The three 

axes are equal, (aa, bb, cc^) and connect the centres of op- 
posite faces. The regular octahedron (fig. 33) consists of 
two equal four-sided pyramids, placed base to base. The six 
solid angles are equal, and so also the edges, which, as in 
the cube, are twelve in number. The plane angles are 60°, 
and the interfacial 109° 28' 16". The axes connect the 
opposite angles ; they are equal and intersect at right angles. 
This class is also called the monometric, (menos, one, and 
metron, measure,) the axes being equal. 

45. The second class includes the square prism (fig. 35) 
and square octahedron (fig. 36.) In the square prism (fig. 
35) the eight solid angles are right angles, and similar, as in 
the cube. The eight basal edges are similar, but differ from 


43. How are the complex forms of crystals arranged and simplified? 
44. Describe the first class of fundamental forms. 






71. — 










' r 

Fig. 37. 

Fig. 38. 

Fig. 39. 

the four lateral. The two basal 
faces are squares, the four lateral 
are parallelograms. The axes con- 
nect the centres of opposite faces, 
and intersect at right angles. 
Square prisms vary in the length 
of the vertical axis, (a, a,) which is 
hence called the varying axis; the Fig * 35 ' Fig * 36 ' 

lateral axes (bb, cc) are equal. This class is also called the 
dimetric, (dis, twofold, and metron, measure.) 

46. The third class contains the rhombic prism, (fig. 37,) 
the rectangular prism, (fig. 38.) and the rhombic octahedron, 
(fig. 39.) The rhom- 
bic prism (fig. 37) has 
two sorts of edges, two 
acute and two obtuse. 
The solid angles are, 
therefore, of two kinds, 
four obtuse and four 
acute. The axes are 
unequal and cross at right angles. The lateral connect the 
centres of opposite edges, bb 9 cc. The basal faces are rhom- 
bic. The rectangular prism (fig. 38) has all its solid angles 
similar. There are three kinds or sets of edges, four lateral, 
four longer basal, and four shorter basal. The axes connect 
the centres of opposite faces, and intersect at right angles. 
The three are unequal. The rhombic octahedron (fig. 39) 
has three unequal axes, connecting opposite solid angles. 
All the sections in this solid are rhombic. This class is 
also called the trimetric, from tru } threefold, and metron, 

47. The fourth class contains the oblique rhombic prism, 
(fig. 40,) and the right rhomboidal prism, (fig. 41.) The 
oblique rhombic prism is represented 
in the figure as inclining away from 
the observer, the prism being in posi- < 
tion when standing on its rhombic 
base. The upper and lower solid 
angles in front are dissimilar, one 
obtuse and the other acute. The four lg * * 

Fig. 41. 

45. What are the forms of the second class ? Describe them. 46. What 
forms make up the third class ? Describe them. 47. What forms does 
the fourth class contain ? How do they differ ? 





lateral solid angles are- similar. Two of the lateral edge* 
are acute, and two obtuse; and the same is true of the basal. 
The lateral axes are unequal; they connect the centres of 
opposite lateral edges, and intersect at right angles. The 
vertical axis is oblique to one lateral axis, and perpendicular 
to the other. The right rhomboidal prism (fig. 41) has two 
obtuse and two acute lateral edges, and four longer and four 
shorter basal edges. The solid angles are of two kinds, 
four obtuse and four acute. The axes connect the centres 
of opposite faces; one is oblique, the others cross at right 
angles. This is also called the monoclinate, (monos, one, 
and clino, to incline,) having one inclined axis. 

48. The fifth class includes the oblique rhomboidal prism. 
^I>. In this solid only those parts diagonally opposite 

d^ «[^| are similar, and consequently it has six kinds of 

k^ *" v* edges. The axes connect the centres of opposite 

^*£^ h faces. They are unequal, and all their inter- 

<Tf T/? sections are oblique. This is called the triclinate 

Z^\ class, from tris, three, and clino, to incline, the 

Fig. 42. th ree axea a n De i n g obliquely inclined. 

49. The sixth class includes the hexagonal prism ("fig. 43) 

and the rhombonedron, 
(figs. 44 and 45.) 
hexagonal prism 

> twelve similar ang^, 
and the same number of 
similar basal edges. The 
lateral edges are six in 

Kg. 43. Kg. 44. **«• number, and similar. 

The lateral axes are equal, and cross at 60°, connecting the 
centres of opposite lateral faces or lateral edges. 

The rhombohedron is a solid whose six faces are all 
rhombs. The two diagonally opposite solid angles (a a) 
consist of three equal obtuse or equal acute plane angles, 
and the diagonal connecting these solid angles is called the 
vertical axis, (a a.) When the plane angles forming the 
vertical solid angles are obtuse, the rhombohedron is called 
an obtuse, (fig. 44,) and if acute, it is called an acute rhom- 
bohedron, (fig. 45.) The three lateral axes are equal, and 

What other names have the first, second, and third classes ? 48. What 
solid is included in the fifth class ? 49. Name the two solids in the sixth 
class of fundamental forms. How are the hexagonal prism and rhombo- 
hedron related? How are rhombohedrons distinguished? 






intersect at angles of 60° : they connect the centres of op- 
posite lateral edges. This will be seen on placing a rhom- 
bohedron in position and looking down upon it from above. 
The six lateral edges will be found to be arranged around 
the vertical axis, like the sides of an hexagonal prism. 

50. The mutual relations of the forms of crystals are well 
shown in the foregoing arrangement. Thus, in each of the 
six classes, the first named solid alone is, properly considered, 
a fundamental form, the others in each class being frequently 
found as secondaries to these. The six fundamental forms 
are the cube, square prism, right rectangular prism, oblique 
rhombic prism or right rhomboidal prism, oblique rhomboi- 
dal prism, and the hexagonal prism or rhombohedron. 

51. The structure of crystals is often seen by lines on 
their surfaces, or by the ease with which the crystal splits 
in certain directions. Common mica cleaves in leaves; 
galena breaks only in cubes, fluor-spar in octahedra, calc-spar 
only in rhombohedrons. This property is called cleavage. 
It does not exist in all crystals, and is not of equal facility 
in all directions. Thus, in mica, cleavage is easy in one 
direction only; while in fluor-spar and calcite it is equally 
easy in three directions respectively. 

Measurement of Crystals. 

52. Common Goniometer.* — The angles of crystals are 
measured by means of instruments called goniometers. £he 
common goniome- 
ter, which is here 
figured, consists of 
a light semicircle 
of brass, (fig. 47,) 
accurately graduat- 
ed into degrees, and 
having a pair of 
steel arms (fig. 46) 
moving on a central 
pivot, and so ar- 
ranged as to slip in 

Fig. 47. 

50. What is said of the relations of fundamental forms ? What six fun- 
damental forms are named ? 51. What is cleavage in minerals ? On what 
does it depend ? Give examples. Is it equal in all minerals? 

* From the Greek, gonia, an angle, and metron, measure. 





Fig. 48. 

a groove over each other. The points a a can thus be made 
to embrace the faces of a crystal whose angle we wish to 
measure. The graduated semicircle is applied with its centre 
at the point of intersection, when the angle is read on tho 
arc. Where the greatest nicety is required, a much more 
delicate instrument is used. 

b6. WoUaston's Reflective Goniometer. — The principle of 
this instrument may be understood by reference to fig. 48, 
which represents a crystal (o) 
whose angle (a b c) is required. 
The eye at P, looking at the face 
(b c) of the crystal, observes a 
reflected image of M in the direc- 
tion of P N. The crystal may 
now be so turned that the same 
image is seen reflected in the next 
face, (6 a,) and in the same direc- 
tion, (P N.) To effect this, the crystal must be turned 
until a b has the present position of b c. The angle d b c 
measures, therefore, the number of degrees through which 
the crystal must be turned. But d b c subtracted from 
180° equals the required angle of the crystal ab c; con- 
sequently, the crystal passes through a number of degrees, 
which, subtracted from 180°, gives the required angle. 

When the crystal is attach- 
ed to a graduated circle, we 
have the goniometer of Wol- 
laston, which is represented 
in fig. 49. The crystal to 
be measured is attached at/, 
and may be adjusted by the 
milled head c and arm d, 
moving independent of the 
great circle a. When adjust- 
ed in the manner described 
above, the wheel is revolved 
until the image of M is seen 
Fig. 49. in the second face. This 

movement is practically a subtraction of the angle a b c 

52. What is a goniometer? Explain the common one and its use. 63. 
Explain the principles of Wollaston's goniometer from figure 48. How 
U this principle used in Wollaston's instrument ? 




from 180°, and the result is read directly by the vernier e. 

— The subject of crystallography cannot be further illustrated 
here; but the learner who desires to pursue it, is referred to 
the highly philosophical treatise on mineralogy by Professor 
J. D. Dana. 

n. LIGHT. 

54. The physical phenomena of light properly belong to 
t!he science of Optics, a branch of natural philosophy not 
necessarily connected with chemistry. A knowledge of some 
of the laws of light is, however, required of the chemical 

55. Sources and Nature of Light. — The sun is the great 
source of light, although we know many minor and artificial 
sources. Of the real nature of light we know nothing. Sir 
Isaac Newton argued that it was a material emanation from 
the sun and other luminous bodies, consisting of particles so 
attenuated as to be wholly imponderable to our means of 
estimating weight, and having the greatest imaginable repul- 
sion to each other. These particles, by his theory, are supposed 
to be sent forth in straight lines, in all directions, from every 
luminous body, and, falling on the delicate nerves of the 
eye, to produce the sense of vision. This is called the New- 
tonian or corpuscular theory of light. It is not generally 
adopted by physicists, but the language of optical science is 
formed mainly in accordance with it. The other view or 
theory of light, which is now almost universally accepted, 
is called the wave or undulatory theory. It is known that 
sound is conveyed through the air by a series of vibrations 
or waves, pulsating regularly in all directions, from the 
original source of the sound. In the same manner it is 
believed that light is conveyed to the eye by a series of un- 
ending and inconceivably rapid pulsations or undulations, im- 
parted from the source of light to a very rare or attenuated 
medium, which is supposed to fill all space. This medium 
is called the luminiferous ether. 

Astronomy furnishes evidence of the presence in space 
of a medium resisting the motion of the heavenly bodies 

54. What is optics ? 55. Name sources of light. What is the New- 
tonian hypothesis ? What is the other theory ? What is the medium of 
light? What evidence does astronomy give of an ether? 



44 LIGHT. 

Encke's comet is found to lose about two days in each sue 
cessive period of 1200 days. Biela's comet, with twice that 
length of period, loses about one day. That is, the succes- 
sive returns of these bodies is found to be accelerated by this 
amount. No other cause for this irregularity has been 
found but the agency of the supposed ether. 

56. Undulations. — The propagation of force by undula- 
tions, pulsations, or waves, is a general fact in physics. A 
vibrating cord communicates its waves of motion to the sur- 
rounding air, and a musical tone results. 

If a long cord A B, fig. 50, 
be jerked by the hand, the 
motion is propagated from 
the hand A, in the curve 

Fig. 50. V A-®> an< * so on successively 

to B, when the motion is 
again reflected in the oppo- 
1 site phase to the hand, as in 
Fi 61 ^ fig. 51, where the continued 

line shows the primary vi- 
brations, and the dotted one that which is reflected. 

A pebble dropped on the surface of a 
quiet pool, produces a series of circular waves 
receding to the shore, (fig. 52.) The waves 
produced do not transport any light bodies 
a accidentally floating on the surface of the 
water. These only rise and fall as each 
Fig. 52. wave p asseg# 

57. The measure of the waves on the surface of water ia 
from crest to crest, or from hollow to hollow, and* in every 

complete wave or entire vibration (fig. 53) 

/^T\ the following parts are recognised : aebdc 

/ V f / * s *^ e whole length of the wave ; aebi the 

^4^ phase of elevation, and bde the phase of dc- 

pression. The height of the wave is ef, and 

g ' * its depth g d. The points in which the phasea 

of elevation and of depression intersect, as in 

fig. 51, are called nodal points, and are always at rest : so 

56. How is force propagated ? Illustrate by figs. 50 and 51. Describe 
the progress of waves from fig. 52. 57. Name the parts of a wave in fig. 
64. Distinguish the phases of elevation and of depression. "What are 
D9dal points? 





that light bodies resting on them would remain undisturbed, 
which placed elsewhere would be immediately thrown off. 
If two waves of equal altitude and arriving from opposite 
directions unite, so that the elevations and depressions of 
the two correspond, then the resulting wave is doubled. 
But if the two meet at half the distance of their respective 
elevations and depressions/so that the crest of one corre- 
spond to the hollow of the other, then both are obliterated, 
and the surface becomes quiet ; or if one wave was larger 
than the other, a third wave, corresponding to the difference 
only of the other two, results. 

58. This is equally true whether we speak of waves of 
sound, of heat, of light, or in fluids. That two waves of 
sound may meet so as to produce silence, may easily be 
shown by vibrating a tuning-fork over an open 
glass A, and holding another similar glass B lip jj 
to lip with the first, and at right angles with it, ( 
as shown in fig. 54. The vibrations may be 
inoreased by sticking a piece of circular card- 
board on one leg of the fork, and by pouring 
water into the first glass until the tone is ad- Fig. 54. 
justed to a maximum. Or a second fork may 

be used in place of B, differing half a tone from the other 
fork, (fig. 55.) In this case a series of swells and cadences 
will be heard in place of entire silence. In these 
cases, the waves of sound interfere, as before, in 
the case of the water. In like manner, two cur- 
rents of thermo-electricity may meet in such a 
manner as to freeze a drop of water in one end of 
the arrangement, the current being excited by 
heating the opposite end of the system. 

59. So two rays of light, AB, CD, fig. 56, Pig w 
meeting at the proper interval, (a,) will produce a 

beam of double intensity ; but if x ^ ^^ ^^ ^-^1, ^ 
they meet at the half interval of ^X^ ' CI^ ' C^* "* 
vibration, darkness results. This m 66 

is interference of light. In mo- 
ther of pearl and many other natural bodies, a beautiful 
play of colors is seen. The microscope reveals on such sur- 

When are waves made double, and when set at rest? 58. Illustrate the 
interference of waves of sound in figs. 54 and 55. What of thermo- 
electricity ? 59. Deicribe the interference df light from fig. 56. 



46 LIGHT. 

feces delicate grooves and ridges, and these are at such dm* 
tances as to produce interference in the light-waves, result* 
ing in partial obscuration and partial decomposition. The 
same effect is artificially produced in medal-ruling. This 
irised effect can be transferred by pressure or copied by the 
electrotype, or even on wax. 

60. The transverse vibrations of a ray of light distinguish 
this from all other modes of undulation or vibration. Dr. 

Bird illustrates this by fig. 57, which represents 
a spherical particle of ether alternately extended 
and depressed at its poles and equator, oscilla- 
ting, or trembling, rather than undulating. 
Thus, each particle in turn communicates the 
Fig. 67. impulse which it receives, and yet the centre 
of each may remain unmoved from its place ; 
as motion in a series of ivory balls causes only the termi- 
nal one to swing, the intermediate ones remaining unmoved. 
In light-waves, the vibration or pendulation of each particle 
is perpendicular to the path of the ray ; and yet the alternate 
effect of the movements of contiguous particles will produce 
a progressive vibration. Thus, in fig. 
!©fc- 58, A B C D may represent particles of 
^b ether in the path of a ray of light, the 
Fig. 58. phases of elevation in A and C and 

those of depression in B and D being 
coincident The fact of the vibrations of light-ether being 
transverse to the path of the ray was first observed by Fres- 
nel. These vibrations are conceived to occur in any or every 
transverse plane. Leaving these interesting generalizations! 
we must briefly recapitulate the well-established 

61. Properties of Light — 1st. Light is sent forth in rays 
in all directions from all luminous bodies. 2d. Bodies not 
themselves luminous become visible by the light falling on 
them from other luminous bodies. 3d. The light which pro- 
ceeds from all bodies has the color of the body from which 
it comes, although the sun sends forth only white light. 4th. 
Light consists of separate parts independent of each other. 
5th. Rays of light proceed in straight lines. 6th. Light 
moves with a wonderful velocity, which has been computed 

What instances are named from nature ? 60. What are transverse vi- 
brations in light ? How is the undulation thus produced ? What i? said 
*f progressive motion ? 61. Enumerate six properties of light. 




by astronomical observations to be at least one hundred and 
ninety-five thousands of miles in a second of time. This 
velocity is so wonderful as to surpass our comprehension, 
Herschel says of it, that a wink of the eye, or a single motion 
of the leg of a swift runner, or flap of the wing of the swiftest 
bird, occupies more time than the passage of a ray of light 
around the globe. A cannon-ball at its utmost speed would 
require at least seventeen years to reach the sun, while light 
comes over the same distance in about eight minutes. 

62. When a ray of light falls on the surface of any body, 
several things may happen. 1st. It may be absorbed and 
disappear altogether, as is the case when it falls on a black 
and dull surface. 2d. It may be nearly all reflected, as from 
some polished surfaces. 3d. It may pass through or be trans- 
mitted ; and, 4th. It may be partly absorbed, partly reflected, 
and partly transmitted. All bodies are either luminous, 
transparent, or opake. Bodies are said to be opake when 
they intercept all light, and transparent when they permit 
it to pass through them. But no body is either perfectly 
opake or entirely transparent, and we see these properties in 
every possible degree of difference. Metals, which are among 
the most opake bodies, become partly transparent when made 
very thin, as may be seen in gold-leaf on glass, which trans- 
mits a greenish-purple light, and in quicksilver, which gives 
by transmitted light a blue color slightly tinged with purple. 
On the other hand, glass and all other transparent bodies* 
arrest the progress of more or less light. 

63. Reflection. — Light is reflected according to a very 
simple law. In fig. 59, if the ray of light fall from F to 
P, it is thrown directly, back to 
F; for this reason, a person 
looking into a common mirror 
sees himself correctly, but his 
image appears to be as far behind 
the mirror as he is in front of it 
The line P F is called the normal. 
If the ray fall from R to P, it will §§ 
be reflected to R/, and if from r, lg ' * 

then it will go in the line /, and so for any other point. 

Illustrate its velocity. 62. What happens to incident light ? How are 
bodies divided in respect to light? Give illustrations of imperfect 
opacity, 63. What is the law of reflection ? What is the normal f 





[f we measure the angles BPF and FPR', we shall find 
them equal to each other, and so also the angles rPF and 
FP/. These angles are called respectively the angles of 
incidence and reflection. We therefore state that the angle 
of incidence is equal to the angle of reflection, which is the 
law of simple reflection. This law is as true of curved sur- 
faces as it is of planes ; for a curved surface (as a concave 
metallic mirror) is considered as made up of an infinite 
number of small planes. 

64. Simple Refraction, — If a ray of light falls perpendi- 
cularly on any transparent or uncrystallized surface, as glass 
or water, it is partly reflected, partly scattered in all direc- 
tions, (which part renders the 
object visible,) and partly trans- 
mitted in the same direction from 
which it comes. If, however, the 
light come in any other than a 
perpendicular or vertical direction, 
as from B to A, on the surface of 
a thick slip of glass, as in fig. 60, 
it will not pass the glass in the 
line BAB, but will be bent or 
refracted at A, to C. As it leaves 
the glass at 0, it again travels in 
a direction parallel to B A, its first course. Refraction, then, 
is the change of direction which a ray of light suffers on 
passing from a rarer to a denser medium, and the reverse. 
In passing from a rarer to a denser medium, (as from air to 
glass or water,) the ray is bent or refracted toward a line 
perpendicular to that point of the surface on which the light 
falls; and from a denser to a rarer medium the law is 

A common experiment, in illustration of this law, is to 
place a coin in the bottom of a bowl, so situated that the 
observer cannot see the coin until water is poured into the 
vessel ; the coin then becomes visible, because the ray of 
light passing out of the water from the coin is bent toward 

Fig. 60. 

What is the angle of incidence ? What of reflection ? What is true 
of curved surfaces ? 64. What is refraction ? Demonstrate the law by 
fig. 60. Which way is the ray bent ? Give a familiar illustration of 




the eye. In the same manner, a straight stick thrust into 
water appears bent at an angle where it enters the water. 

65. Index of Refraction. — The obliquity of the ray tq tho 
refracting medium determines the amount of refraction. The 
more obliquely the ray falls on the surface, the greater tho 
amount of refraction. A little modification of the last figure 
will make this clear. Let R A 
(fig. 61) be a beam of light falling 
on a refracting medium : it is bent 
as before to B/. If we draw a circle 
about A as a centre, and let fall 
the line a a, from the point a, ' 
where the circle cuts the ray E, 
and at right angles to the normal 
A r A, the line a a is called the sine 
of the angle of incidence ; while 
the line a' a' is catted die sine of 
the angle of refraction. 

If a more oblique ray r cuts th* circle at b, the line b b 
will be longer than the line a a, inasmuch as the angle b A 
a is greater than the angle a A a. 

The line measuring the obliquity before refraction, when 
the ray passes into a denser medium, is always greater than 
that which measures it after. The ratio of these lines ex- 
presses the refractive power of the medium. This is called 
the index of refraction. 

In rain water the ratio of these lines is as 529 : 396 or 
1*31 ; in crown glass it is as 31 : 20 or 1*55; in flint glass 
1-616, and in the diamond 2-43. 

66. Substances of an inflammable nature, or rich in carbon, 
and those which are dense, have, as a general thing, a higher 
refracting power than others. Sir Isaac Newton observed 
that the diamond and water had both high refracting 
powers, and he sagaciously foretold the fact, which chemis- 
try has since proved, that both these substances had a com- 
bustible base, or were of an inflammable nature. 

67. Prism. — In the cases of simple refraction just ex- 
plained, the ray, after leaving the refracting medium, goes 
on in a course parallel to its original direction, because the 

65. What is the index of refraction ? Demonstrate this from fig. 61. 
66. What substances have highest refraction ? What was New ton'* sug- 
gestion about the diamond ? 





Fig. 02. 

^b' two surfaces of the medium are pa- 
rallel. If, however, the surfaces of the 
refracting medium are not parallel, 
the raj, on leaving the second sur- 
face, will be permanently diverted 
from its original path. % The com- 
mon triangular glass prism (fig. 62) illustrates this. 
As already explained, the ray K is bent toward the 
normal in media more dense than air. But in the 
prism the emergent ray R is, by the same law, 
still farther refracted in the direction R'. By 
altering the form of tho surfaces, we may thus 
send the ray in almost any. direction, as in the 
common multiplying-glass, which gives as many 
images as it has surfaces of reflection. In this 
way it is that concave metallic mirrors concentrate, 
and convex ones disperse a beam of light. Fig. 63 
shows the prism conveniently mounted for use. 
_____ 68. Analysi&of Light. — By means of the prism, 
Pig. 63. ^* r ^ saao Newton demonstrated the compound na- 
* ture of white light, such as reaches us in the ordi- 
nary sunbeam. In 
fig. 64 a pencil of 
rays from R, fall- 
ing from a small 
circular aperture 
in the shutter of a 
darkened room on 
Fi & 64# a common trian- 

gular prism, is refracted twice, and bent upward toward the 
white screen R', placed at some distance from the prism, 
where it forms an oblong colored image, composed of seven 
colors. This image is called the prismatic or solar spectrum. 
The spectrum has the same width as the aperture admit- 
ting the beam of light, but its length is greatly increased be- 
yond its diameter, the ends retaining the rounded form of 
the opening. This image or spectrum presents the most 
beautiful series of colors, exquisitely blended, and each pos- 
sessing a degree of intensity, splendor, and purity far ex- 
ceedingly the colors of the most brilliant natural bodies. 
These colors are not separated by distinct lines, but seem to 

67. How is light refracted by surfaces not parallel What is tho prism 2 






melt into one another, so that it is impossible to say where 
one ends and the next begins. 

The light from flames of all kinds, the oxy-hydrogen 
blowpipe, and the electrio spark, or galvanic light, is also 
compound in its nature, like that of the sun and other ce- 
lestial bodies. 

69. Prismatic Colors. — The colors of the solar spectrum 
are in the following order, reading upward : red, orange, yel- 
low, green, blue, indigo, violet. These colors are of very 
different refrangibility, and for this reason are presented in 
a broad and blended surface, the red being the least refracted, 
and the violet the most. The seven colors of Newton, it 
is believed, are really composed of the three primitive ones, 
red, yellow, and blue. This idea is well expressed in th« 
following diagram, 
(pg. 65.) The three 
primitive colors 
each attain their 
greatest intensity 
in the spectrum at 
the points marked 
at the summit of 
the curves; while 

the four other co- Fi * 65 ' 

lors, violet, indigo, green, and orange, are the result of a 
mixture, in the spectrum, of the first three. A portion of 
proper white light is also found in all parts of the spectrum, 
which cannot be separated by refraction. We may hence 
infer that there is a portion of each color in every part of 
the spectrum, but that each is most intense at the points 
where it appears strongest. The light is most intense in the 
yellow portion, and fades toward each end of the spectrum. 

Sir John Herschel has detected rays of greater refrangibi- 
lity than the violet of the spectrum and are beyond it, which 
have a lavender color. They have this color after concen- 
tration, and are therefore not merely, as might be supposed, 
dilute violet rays. 

If the spectrum is formed by a- beam of light passing 
through a slit not over ^th of an inch in width, the image 

68. Describe the analysis of light What is the image called ? What 
is the form of the spectrum ? How are the colors arranged ? Describe 
the blending of the colors from fig. 65. What is lavender light? 



62 LionT. 

will be crossed by a great number of dark lines, which al- 
ways appear in the same relative position. They are called 
the fixed lines of the spectrum, and are much referred to 
as boundary lines in optical descriptions. 

70. Each of the prismatic colors has some other, which 
blended with it produces white light, and hence 
is called its complementary color. Let indigo be 
regarded as a deeper blue, and each of the three 

' primary colors has its secondary colors. Fig. 
65 shows the three primary tints blending to 
Fig. 65 {bit.) f orm w hite light at the centre : at the other 
parts the complementary colors are opposite to each other, 
e, g. red and green, blue and yellow. 

71. Double refraction of light is a phenomenon ob- 
served in many crystalline transparent bodies, and is due to 
their peculiar structure. It is also seen in bone, shell, horn, 
and other similar substances. The beam of light in passing 
through such bodies is split into two portions, each of which 
gives its own image of any object seen through the doubly 
refracting substance. In calcite, carbonate of lime, or Ice- 
land-spar, this phenomenon is beautifully seen. 

A sharp line, like pq, fig. 66, 
when seen through a rhomb of calc- 
spar, in the direction of the ray R r, 
will seem to be double, a second 
parallel line m w, being seen at a 
short distance from it, and the dot 
o will have its fellow e. In this 
Fig. 66. ^gg tne xigHt is represented as com- 

ing from E to r, and, passing through the crystal, it is split 
and emerges in two beams at e and o. The same effect 
would be produced if the light fell so as to strike any part 
of the imaginary plane ACBD, which divides the crystal 
diagonally and is called its principal section. The axis or 
line drawn from A to B is contained in this plane. But 
if we look through the crystal in a direction parallel to this 
plane (ACBD) there is only simple refraction, and only 
one line is seen. One of these beams is called the ordinary 
and the other the extraordinary ray. In the case of crys- 
tallized minerals, this result is due to the naturally unequal 

What lines are seen in the spectrum? 70. What of the colors of na- 
tural bodies ? 71. What is double refraction ? Describe fig. 66. What is 
the ordinary ray ? Which the extraordinary ? What relation has this 
phenomenon to crystallization ? 




elasticities of the molecules in the crystals — and it is ob- 
served only in those minerals whose molecules are ellipsoidal 
— and is wanting in those, like fluor-spar, &c, which belong 
to the cube and its derivatives, in which the molecules are 
spherical. In well annealed glass, by mechanical pressure, a 
sufficient separation of the two rays may be produced to cause 
color by interference, though not enough to cause two images 

72. Polarization. — The light which has passed one crys- 
tal of Iceland-spar by extraordinary refraction is no longer 
affected like common light. If we attempt to pass it through 
another crystal of the same substance, there will be no fur- 
ther subdivision, and only a greater separation of the two 
beams. This peculiarity of the extraordinary ray is called 
polarization. This interesting phenomenon was accident- 
ally discovered in 1808 by Malus, while looking through 
a doubly-refracting prism at the light of the setting sun, 
reflected from the surface of a glazed door standing at an 
angle of about 56° 45', which is the angle at which glass 
polarizes light, by reflection. 

It is the peculiarity of light which has been polarized 
that it will no longer pass through certain substances which 
are transparent to common light. Many crystalline sub- 
stances possess the power of polarizing light. The mineral 
called tourmaline has this property in a remarkable degree. 
The internal structure of this mineral is such that a ray of 
light which has passed through a thin plate of it cannot pass 
through a second, if it is placed in a position at right angles 
with the first. 

For example, in 
the annexed figure 
(67) we have two R 

thi n plates of tour- — — ' | 
maline placed pa- 
rallel to each other 
in the same direc- 
tion. A ray of Fig. 67. Fig. 68. 
light passes through 

both, in the direction of R R', and apparently suffers 
no change : if, however, these plates are so placed as to 
cross each other at right angles, as in fig. 68, the ray of light 

72. What is polarization ? Who discovered this phenomenon ? What is 
the peculiarity of polarized light? Illustrate this from the tourmaline. 





Fig. 70. 

is totally extinguished ; and two such points may be found 
in revolving one of the plates about the ray as an axis. 

73. For illustration, we may suppose the structure of 
this mineral to be such that a ray of light 
can pass between the ranges of particles in 
we direction only, as a fiat blade may pass 
between the wires of a bird- 
cage, fig. 69, if placed pa- 
rallel to them; but will be 
arrested by the bars, if presented at right 
angles to the wires. 

Light is polarized in many ways, as, for 
example, by passing through a bundle. of 
plates of thin glass or of mica, as in fig. 70, 
by reflection from the surface of unsilvered 
glass, of a polished table and of most polished 
non -metallic surfaces, and at a particular 
angle for each. This is plane polarized light 
74. The beautiful phe- 
nomenon of circular and 
elliptic polarization is 
seen in many crystalline 
bodies. Plates of quartz, 
a mineral having one axis, 
show the prismatic co- 
lors, when viewed by po- 
larized light, arranged in 
circles and a cross, as in fig. 71; 
and by the revolution of the 
plane of polarization through 90°, 
the colors are changed, and a light 
cross (fig. 71) occupies the plane 
of the dark one. Nitre gives two 
axes of polarization, which in the 
revolution of the plane show the 
changes seen in figures 73 and 
74. Uniaxial crystals uniformly 
Fig. 73. Fig. 74. give circular, and binaxial onoa 

elliptical figures. 

Fig. 71. 

Fig. 72. 

When is the ray extinguished ? 73. How is this phenomenon explained 
in reference to the structure of the crystal? In what ways is light po- 
larized? 74. What crystalline bodies give circular, and what elliptical 
polarization ? Illustrate this from quartz and nitre. 





75. The chemical power of the son's rays is seen in the 
blackening of chlorid of silver, which Scheele long ago observed 
to take place much more rapidly in the violet ray than in 
any other part of the solar spectrum. It was afterward 
observed by Bitter that this blackening likewise occurred 
beyond the violet ray, apparently in the dark. 

The researches of Neipce, Daguerre, and others, have 
greatly enlarged the boundaries of our knowledge on this 
subject, and given to the world the elegant arts of the 
daguerreotype and photography. The darkening of metallic 
salts by light is owing to a peculiar class of rays in the 
spectrum, called by Dr. Herschel the chemical ray*, which 
are diffused indeed in all parts of the spectrum, but which 
are concentrated with more power beyond the violet. This 
influence has also been variously denominated actinism! 
energia, and tithonicity. 

76. The accompanying diagram (fig. 75) will enable the 
student to comprehend this subject as at present understood. 
From A to B we have the solar 
spectrum, with the colors in the 
same order as already described. 
The cl emical power is greatest 
at the violet, and the greatest 
heat at the red ray. At b 
another red ray is discovered, LA ™"> ra i 
and at a is the lavender light. YloLW 
The luminous effects are shown ^j,^ 
by the curved line C, the maxi- blot, . . . 
mum of light being found at greet, . , 
the yellow ray. The point of yellow, • . 
greatest heat is at D, beyond JJ^;; 
the red ray, and it gradually 
declines to the violet end, 
where it is entirely wanting, 
the other limit of heat being 
at c. The chemical powers 
are greatest about E, in the 
limits of the violet, and gra- 
dually extend to d, where they 
arc lost. They disappear also 

Fig. 75. 

75. What is the chemical power of the sunbeam ? 70. Illustrate th« 
relations of the chemical and other rays, from fig. 75. 




entirely at C ; 4be yellow ray, which is neutral in this re- 
spect, attains another point of considerable power at F, in 
the red ray, which gives its own color to photographic pic- 
tures, and disappears entirely at e. The points D, C, E, there- 
fore represent respectively the three distinct phenomena of 
Heat, Light, and Chemical Power. This last is. believed to 
be quite independent of the other powers ; for all light may 
be removed from the spectrum by passing it through blue 
solutions, and yet the chemical power remains unaltered. 

77. It will readily be perceived that these phenomena 
connected with the sunbeam exert no inconsiderable or 
unimportant influence in the order of events, whether as 
connected with the development of life on our planet, or 
with those great physical changes which depend on the 
calorific and magnetic agencies that seem inseparably con- 
nected with the light and heat of the sun. Plants can 
decompose carbonic acid and carry on the functions of 
nutrition only under the power of solar light; and the yellow 
ray has been shown by Br. Draper to be the one by whose 
agency this change is effected in the vegetable kingdom. 

78. Phosphorescence is a property possessed by some bodies 
of emitting a feeble light, often at ordinary temperatures. 
The diamond and some other substances, after being exposed 
to the rays of the sun, will emit light for some time in the 
dark. Fluor-spar, feld-spar, and some other minerals, give 
out a fine light of varied hues, when gently heatea or 
scratched. Oyster-shells which have been calcined with 
sulphur and exposed to the sunlight, will shine in a dark 
place for a considerable time afterward, and even an electrical 
spark will renew this emanation. The glow-worm, the fire- 
fly, rotten wood, decaying fish, and various marine animals 
possess the same power, although in these cases the cause is 
probably different from that which excites the same pheno- 
menon in crystallized bodies. 

77. "What consequences follow the phenomena described? 78. What if 
pho*i>horescence ? 



HEAT. 57 

Sources and Properties of Heat 

79. The phenomena of Heat, or Caloric, are emineLtly 
interesting to the chemical student. They may be discussed 
under two general divisions: 1. The Physical; and, 2. The 
Chemical. Under the first head are included the communi- 
cation of heat, by radiation, by conduction, and convection ; 
the transmission of heat by various substances, and the 
phenomena of expansion, including thermometers and pyro- 
meters ; and lastly, specific heat. Under the second head are 
placed the changes produced by heat in the states of bodies ; 
for example, liquefaction and latent heat of liquids, vapor- 
ization and latent heat of vapors, liquefaction of gases, 
natural evaporation and congelation, density of vapors, and 
so forth. 

80. The sources of heat are chiefly the sun, combustion, 
and chemical changes; friction, electricity, vitality; and, 
lastly, terrestrial radiation. 

Solar heat, as is well known, accompanies the sun's light, 
and it unquestionably results from the intensely high tem- 
perature of the sun itself. It is believed that the sun's 
rays do not heat the regions of space, and the earth's 
atmosphere 'is heated almost entirely by contact with the 
surface of the heated earth. A portion of the sun's heat is 
however taken up by the air before the rays reach the earth. 

Combustion and chemical change, including vital heat, 
are sources of heat, limited by the quantity of matter suffer- 
ing change, and to the time in which the change takes place. 
The stores of fossil fuel laid up in the coal formations and 
the vegetable combustibles now on the earth's surface may 
be considered as a result of the sun's action through the 
powers of vegetable life. 

Friction causes heat, as a result of mechanical motion. 
The heat of friction continues as long as the mechanical 
power required to produce motion is maintained. No 
change of state or loss of weight is necessarily experienced 

79. What is said of heat? How is the subject discussed? 80. What 
are the sources of heat ? What of solar heat ? What of combustion ? 
What of friction? 



68 HEAT. 

in the substances employed. Count Rumford showed that 
in the boring of cannon under water, the heat evolved was 
so considerable as to bring the water, in a short time, to the 
boiling-point The same observer succeeded in warming a 
large building by the heat evolved from the constant move* 
ment of large plates of cast-iron upon each other. Friction- 
heat may be regarded as the equivalent of the motion pro* 
ducing it The heat of the electrical spark and of the 
galvanic current will be considered elsewhere. 

81. Terrestrial radiation is a constant source of heat, 
escaping from the interior of the earth, and has doubtless 
some effect in modifying the climate of our globe. Geolo- 
gists consider it proved that the earth has cooled to its pre- 
sent condition from a state of intense ignition, and that this 
state still remains in the interior, at no very considerable 
distance from the surface. All deep mines and Artesian 
wells show a constant and progressive increase of temperature 
in going down, and below the line of atmospheric influence. 
The Artesian well in the yard of the great Grenelle slaughter- 
house, in Paris, is 2000 feet deep, and the water rises with a 
temperature of 85° degrees Fahrenheit. At Neusalzwerke, 
in Westphalia, is a well 2200 feet deep, and its water has a 
temperature of 91°. The average increase of temperature 
from this cause is estimated to be 1°8, for every hundred 
feet of descent. Assuming this ratio, we shall have at two 
miles the boiling-point of water ; and at about twenty-three 
miles, or only T g th of the earth's radius, there must be a 
temperature of near 2200 degrees of Fahrenheit At this 
heat, cast-iron melts, and trap, basalt, obsidian, and other 
rocks are perfectly fluid. The geological importance of these 
facts is self-evident ; and we cannot fail to remark here an 
efficient cause for all hot-springs. 

82. Properties of Heat — Heat is invisible and impon- 
derable. It proceeds, like light, in rays, with great but 
hitherto undetermined velocity. The intensity of heat-rays 
varies inversely as the square of the distance . from the 
source of heat. Kays of heat, like those of light, may be 
concentrated from a metallic mirror, but not from those of 
glass, as this substance absorbs heat very largely. They are 

81. What is said of terrestrial radiation ? What is determined in deep 
wells? What is the rate of increase ? At what depth would iron melt? 
32. What are the properties of heat? How is it like light? 




also of various refrangibility, and capable of double refrac- 
tion and polarization. Therefore, they move in waves 01 
undulations. Heat is self-repellant, as two bodies heated in 
vacuo repel each other. It is communicated by conduction 
and by convection as well as by radiation. It is variously 
absorbed and transmitted by various substances, and pro- 
duces different degrees of expansion, varying with the nature 
of matter affected. Lastly, it determines the phenomena 
of congelation, liquefaction, and vaporization. The physio- 
logical sensation of cold and heat experienced in our per- 
sons is not to be confounded with the physical and chemical 
phenomena of heat now to be discussed. This sensation is, 
within certain limits, entirely relative. For example, if one 
hand is plunged in a vessel of iced-water and the other into 
moderately warm water, a strong contrast is evident imme- 
diately ; but if we suddenly transfer both hands to a third 
vessel of water, at the common temperature, our sensations 
are instantly reversed. The third vessel is warm as com- 
pared with ice-water, and cold compared with the tepid 

Communication of Heat. 

83. Heat is communicated from a hot body, 1. By radia- 
tion, or transmission of rays of heat in all directions ; 2. 
By contact of the atmosphere conveying it away, (convec- 
tion ;) and, 3. By communication to the substance support- 
ing it, (conduction.) By one or all these modes, a body 
placed in vacuo or in the air, and differing in temperature 
from surrounding bodies, gradually regains the equilibrium 
of temperature. If hot, it loses, and surrounding bodies 
gain ; if cold, it gains at the expense of those substances 
having a higher temperature. 

84. Radiation takes place from all bodies wherever there 
is a disturbance of equilibrium, but in very various degrees, 
according to the nature of the body and of its surface. All 
bodies have a specific radiating and absorbing power in 
respect to heat. To these the retaining and reflecting 
powers are strictly opposed. Radiation takes place in a 
vacuum more easily than in air, and is, therefore, quite 

WTiSt i» said of the sense of heat and eold? Give an illustration. 
S3. How is heat communicated ? 84. How does radiation happen ? 





independent of any conducting medium. 
Rays of heat may be concentrated by the 
parabolic metallic mirror. All rays of 
heat or light falling on this form of mirror 
are collected at F, the focus, (fig. 76,) and 
a hot body placed there will have its rays 
sent forth in parallel straight lines, as 
shown in the figure. A second and similar 
mirror may be so placed as to receive and 
collect in a focus all the rays proceeding 
from any body in the focus of the other, 
Fig. 76. where they will become evident by their 
effect on the thermometer. If the hot body be a red-hot 
cannon-ball, and the mirrors are carefully adjusted, so as to 
be exactly opposite each other in the same line, the accumu- 
lation of heat in the focus of the second mirror is such as 
to inflame dry tinder, or gunpowder, even at many feet 

85. This striking experiment is shown by the conjugate 

mirrors, arranged as 
in fig. 77. Ice placed 
in the focus of one of 
the mirrors will de- 
press a thermometer 
in the other focus, — 
not because cold is 

__ radiated, (as cold is 9 
Fl S-^* mere negation,) but 

because in this case the thermometer is the hot body and 
parts with its heat to fuse the ice. A thermometer sus- 
pended midway between the two mirrors is not affected. A 
plate of glass held between the mirrors will cut off the calorific 
rays — thus proving a difference of penetrating power be- 
tween the rays of heat and of those of light. As soon aa 
the screen is raised the phosphorus in the focus is inflamed. 

86. Radiation and Absorption of heat are exactly equal 
to each other in a given • surface, but, as before stated, 
the nature of the substance and of the surface have much 
influence in these respects. All black and dull surfaces ab- 
sorb heat very rapidly when exposed to its action, and part 

How does a metallic mirror affect heat ? 85. Describe the experiment 
tn fig. 77. 86. What of absorption? How does color affect it? 




with it again by secondary radiation. The sun shining on 
a person dressed in black is felt with much more power than 
if he were dressed in white. The former color rapidly 
absorbs heat, while from the latter a considerable part of it 
is reflected. The color of bodies has, however, nothing to 
do with their radiating powers, and one colored cloth is as 
warm in winter as another, as regards the emission of heat. 

If the radiating power of a surface covered with lamp- 
black be assumed as 100, that of a surface covered with 
Indian ink will be 88, with ice 85, with graphite 75, with 
dull lead 45, with polished lead 19, with polished iron 15, 
with polished tin, copper, silver, or gold, 12. (Leslie.) 
Hence the polished metallic vessel, which is so well adapted 
to retain the heat of boiling water, is the very worst vessel 
in which to attempt to boil it. The sooty surface next the 
fire, however, transmits heat with the greatest rapidity. In 
the experiment with the mirrors just described, the polished 
surfaces remain cool, reflecting nearly all the heat which 
falls upon them. A glass mirror in the same experiment 
would be useless, as glass absorbs nearly all the heat, of low 
intensity, which falls upon it. 

87. The formation of dew is owing to radiation, cooling 
the surface of the earth so rapidly, that the moisture of the 
air, which is always abundant in summer, is condensed upon 
it : as we see it on the outside of a tumbler of iced-water in 
a hot day. Radiation takes place more rapidly from the 
surface of grass and vegetation than from dry stones or 
dusty roads : for this reason, plants receive abundant dew, 
while the barren sand has none. 

88. Conduction of heat. — A metallic bar placed by one 
end in the fire, slowly becomes hot, the heat being trans- 
mitted by conduction, from particle to particle. Each so- 
lid has its own peculiar rate of conducting heat, but 
in all it is a progressive operation, the heat seeming to 
travel with greater or less rapidity, according to the nature 
of the solid. If we hold a pipe-stem or glass rod in the 
flame of a spirit-lamp or candle, we can heat it to redness 
within an inch of our fingers without inconvenience ; but a 
wire of silver or copper held in the same manner soon be- 

Give some results of radiation from different substances. 87. How it 
dew formed ? 88. What is conduction ? Why docs it fall on plants ? 



62 HEAT. 

comes too hot to hold. This is owing to an inherent di£ 
ference in these solids, which we call conducting power. The 
. progress of conducted 

~ ° ° c ° IT heat in a 80lid is ea8i " 

W ly shown, as in fig. 78, 
e ' representing a rod of 

copper, to which are stuck by wax several marbles at equal 
distances ; one end is held over a lamp, and the marbles 
drop off, one by one, as the heat melts the wax; that 
nearest the lamp falling first, and so on. If the rod is of 
copper, they all fall off very soon ; but if a rod of lead or 
platinum is used, the heat is conveyed much more slowly. 
Little cones of various metals and other substances may be 
tipped with wax or bits of phosphorus, as 
shown in fig. 79, and placed on a hot surface. 
The wax will melt, or the phosphorus inflame, 
at different times, according to the conducting 
Pig. 79. p 0wer f the various solids. A screen is 
needed to cut off the radiant heat, which would otherwise in- 
flame the phosphorus prematurely. Accurate experiments 
have been made, which have enabled us to arrange most so- 
lids in a table showing their conducting powers. The metals, 
as a class, are good conductors, while wood, charcoal, fire-clay, 
and similar bodies are bad ones. Thus gold is the best con- 
ductor, and may be represented by the number 1000 ; then 
marble will be 23*5, porcelain 12, and fire-clay 11. Metals, 
compared with each other, are very different in conducting 
power. Thus — 

Gold 1000 

Silver 973 

Copper 898 

Platinum. 381 

Iron 375 

Zinc 363 

Tin 304 

Lead 180 

89. Vibrations occur in masses of metals and other sub* 
stances when conducting heat, which seem to indicate the 
production of waves or undulations among the particles. 
Mr. Trevellyan has remarked that if a mass of warm brass 
is placed on a support of cold lead, the rounded surface of 

What is its rate in different substances ? 89. How is an undulation 
proved to exist in heated bodies ? Mention Trevellyan and Page's ex- 




the brass resting on the flat surface of the lead, the brass 
bar is thrown into a series of vibrations, accompanied by 
a distinct sound and a rocking motion. of the brass, until 
equilibrium is restored. Dr. Page has shown that a current 
of galvanic electricity passed through a similar apparatus 
produces the same results. Fig. 
80 shows Page's apparatus, in 
* which a feeble current of electri- 
: city produces a rocking motion of 
' the metallic masses resting on the 
bars of brass. The best effects are 
Fig. 80. produced between good and bad 

conductors of heat, the former being the hot bodies. 

90. Heat is conducted in crystallized bodies, in curves 
springing from the sources of heat. In plates of homoge- 
neous substances these curves are circles ; in those of a crys- 
talline texture, belonging to the rhombohedral system, the 
curves are ellipses of very exact form, whose longer axes are 
in the direction of the major crystalline axis — proving the 
conducting power of such bodies to be greatest in that direc- 
tion. The mode of experimenting in such cases is to cover 
the surface of the crystalline plate with wax, heat very gra* 
dually, and watch the lines of fusion on the surface. 

91. The sense of touch gives us a good idea of the dif- 
ferent conducting power of various solids. All the articles 
in an apartment have nearly the same temperature ; but if 
we lay our hand on a wooden table, the sensation is very dif- 
ferent from that which we feel on touching the marble 
mantel or the metal door-knob. The carpet will give ua 
still a different sensation. The marble feels cold, because it 
rapidly conducts away the heat from the hand j while the 
carpet, being a very bad conductor, retains and accumulates 
the heat, and thus feels warm. Clothing is not itself warm, 
but, being a bad conductor, retains the heat of the body. A 
film of confined air, is one of the worst Conductors; loose 
clothes are therefore warmer than those which fit closely. 
For the same reason, porous bodies, like charcoal, are bad 
conductors ; and a wooden handle enables us to manage hot 
bodies with ease. 

92. The conducting power of fluids is very small. A 

90. How is heat conducted in crystals ? 91. What does touch inform 
ns of? 92. What of the conducting power of fluids ? 





simple and instructive experiment will prove this satis- 
factorily. A glass, like that in fig. SI, 
is filled nearly to the brim with water. 
A thermometer-tube, with a large ball, 
is so arranged within it that the ball 
is just covered with the water: the 
stem passes out at the bottom through 
a tight cork, and has a little colored 
fluid, L, in it, which will, of course, 
move with any change of bulk in the 
air contained in the ball. 

Thus arranged, a pointer I marks 
exactly the position of one of the drops 
) of enclosed fluid, when a little ether is 
poured on the surface of the water, 
and set on fire. The flame is intensely 
hot, and rests on the surface of the 
water; the column of fluid at I is, 
however, unmoved, which would not 
be the case if any sensible quantity of 
heat had been imparted to the water. 
The warmth of the hand touching the 
ball will at once move the fluid at I, 
by expanding the air within. By heat- 
ing a vessel of water on the top, then, 
s we should never succeed in creating any 
] thing more than a superficial elevation 
' of temperature : at a small depth the 
Fig. 81. water would remain cold. Liquids do 

possess a very low conducting power, contrary to the opinion 
of Count Rumford, and heat appears to be propagated in 
them by the same law as in solids, when care is taken to 
avoid the production of currents. 

93. The conducting power of gases is also very small. 
Heat travels with extreme slowness through a confined 
portion of air. This is a very different thing from the con- 
vection of heat in gases, which we will presently explain. 
Double windows and doors, and furring (so called) of plas- 
tered walls, afford excellent illustrations of the slow con- 
duction of heat through confined air. Wc have no proof 
that heat can be conducted in any degree by gases and va« 

Explain the experiment, fig. 81. What of the conducting power of gases t 





pors. To illustrate the relative conducting powers of solids, 
fluids, and gases : if we touch a rod of metal heated to 120°, 
we shall be severely burned ; water at 150° will not scald, 
if we keep the hand still, and the heat is gradually raised ; 
while air at 300° has been often endured without injury. 
The oven-girls of Germany, clad in thick socks of woollen, 
to protect the feet, enter ovens without inconvenience whero 
all kinds of culinary operations are going on, at a tempera- 
ture above 300° ; although the touch of any metallic article 
while there would severely burn them. 

94. Convection of heat is its transportation, as in liquids 
and gases, by the power of currents. 
Heat applied from beneath to a vessel 
containing water, warms the layer or 
film of particles in contact with the 
vessel. These expand with the heat, 
and consequently, becoming lighter, 
rise, and colder particles supply their 
place, which also rise in turn, and 
so the whole contents of the vessel 
come in quick succession into con- 1 
tact with the source of heat, and 
convey it through the mass. This 
is well illustrated in fig. 82, which 
shows how water acts in a vessel of 
glass, when heated at a point be- 
neath by a spirit-lamp. Each par- 
ticle in turn comes under the in- 
fluence of heat, because of the per- 
fect mobility of the fluid. A series 
of such currents exists in every 
vessel in which water is boiled, and 
they are rendered more evident by throwing into it a few 
grains of some solid (like amber) so nearly of the same 
gravity of water that it will rise and fall with the currents. 

95. In the air, and in all gases and vapors, the same 
thing happens. The earth is heated by the sun's rays, and 
the Sim of air resting on the heated surface rises, to be re- 
placed by cold air. The rarefied air may be easily seen, on 
a hot day, rising from the surface of the earth, being made 

Fig. 82. 

94. What is convection ? Illustrate it in water. 95. How is heat distri 
outed in air. 






visible b> its different refractive power. Hence arise man? 
aerial currents and winds. The currents of the ocean art 
also influenced by the same cause. 

Transmission of Heat. 

96. Light passes through all transparent bodies alike, 
from what source soever it may come. The rays of heat 
from the sun also, like the rays of light from the same lu- 
minary, pass through transparent substances with little 
change or loss. Radiant heat, however, from terrestrial 
sources, whether luminous or not, is in a great measure ar- 
rested by many transparent substances. If the sun's rays be 
concentrated by a metallic mirror, the heat accompanying 
them is so intense at the focus as to fuse copper and silver with 
ease. A pane of colorless window-glass interposed between 
the mirror and the focus, will not stop any considerable part 
of the heat. If the same mirror is presented to any other 
source of heat, however, (as, for example, to the red-hot ball, 
85,) the glass plate will stop nearly all the heat, although 
the light is undiminished. We thus distinguish two sorts of 
calorific rays, which are sometimes called Solar and Culinary 
Heat; and we discover that substances transparent to light 
are not, so to speak, transparent to heat in a like degree. 
This property is distinguished from transparency by the term 
Diathermancy y (meaning the easy transmission of heat.) It 
appears that many substances are eminently diathermous, 
which are almost opake to light; like smoky quartz, for 
example. The temperature of the source of heat has the 
greatest influence on the number of rays of heat which are 
transmitted by a given screen ; as in the case of the glass 
plate, which permits nearly all the sun's rays to pass, but 
arrests over 65 per cent, of the rays from a lamp-flame. 

97. Our knowledge on this subject has been derived almost 
entirely from the researches of M. Melioni, of Naples. This 
philosopher, by the use of a peculiar apparatus, called the 
thermo-electric pile, was able to detect differences of tempera- 
ture altogether inappreciable by common thermometers. Thif 
instrument is an arrangement of little bars of the two metals, 

96. Distinguish transmission of heat from that Qf light. What if 
diathermancy ? What was Melloni's research ? 





Fig. 83. 

antimony and bismuth, about fifty of which are sol- 
dered together by their alternate ends, the whole 
being, with its case, not more than 2} inches long, 
by J to t of an inch in diameter. The least differ- 
ence of heat between the opposite ends of this little 
battery will produce an electrical current capable of influenc- 
ing a magnetic needle in an instrument called a galvanomC' 
fer,(§202.) The needle of the galvanometer will move in exact 
accordance to the intensity of the heat. This is so delicate 
an instrument, that the radiant heat of the hand held near 
the battery will cause the needle to move some 10° over its 
graduated circle. In fig. 84, a is the source of heat, (an oil- 

Pig. 84. 

lamp in this case,) b a screen having a hole to admit the 
passage of a bundle of rays; c is the substance on which the 
heat is to fall ; d the thermo-multiplier, or battery, which is to 
receive the rays after they have passed through the substance 
c. Two wires connect the opposite members of this battery 
with the galvanometer e, which, for steadiness, is placed on 
a bracket attached to the wall. Thus arranged, and with 
various delicate aids which we cannot here explain, a vast 
number of most instructive experiments have been made on 
radiant heat from different sources, and its effect ascertained 
on various substances. Four different sources of heat were 
employed : 1. The naked flame of an oil-lamp ; 2. A coil of 
platinum wire heated to redness by an alcohol-lamp; 3. A 
surface of blackened copper heated to 734°; and, 4. The 
same heated to 212° by boiling water. The first two of 
these are luminous sources of heat, the last two non-luminous. 
98. As already stated, the temperature of the source 

97. What are Mellonfs researches? Describe the arrangement in figs. 
83 and 84. 





greatly influences the number of rajs transmitted. Thai 
which has passed through ono plate of rock-salt has less 
liability to be arrested by a second, still less by a third, and 
so on. 

The following table will show a few of the principal re- 
sults : — 

Names of interposed substances, common 
0.102 inch. 

Transmission of 100 
rays of heat from 



Rock-salt, transparent and colorless... 




Rock-crystal, brown 

Alum, transparent 

Sugar-candy , 

Ice, pure and transparent 

Thus it appears that rock-salt is the only substance which 
permits an equal amount of heat from all sources to pass. 
In other cases, the number of rays passing seem proportioned 
to the intensity of the source. M. Melloni has called rock- 
salt the glass of heat, as it permits heat to pass with the same 
ease that glass does light. It is supposed that the difference 
found by experiment in the diathermancy of bodies is owing 
to a peculiar relation which the various rays of heat sustain 
to these bodies, analogous to that difference in the rays of 
light which we call color. Thus all other bodies, except salt, 
act on heat as colored glasses act on light, entirely absorbing 
some of the colors, and allowing others to pass. In this 
view, rock-salt may be said to be colorless as respects heat, 
while alum and ice are in the same sense almost back. 
Opake bodies, like wood and metals, entirely prevent the 
transmission of heat ; but dark-colored quartz crystal is seen, 
by the table, to differ only 1 from white crystal, and even 
perfectly black glass does not entirely stop all heat. 

99. By cutting rock-salt into prisms and lenses, the heat 
from radiant bodies may be reflected, refracted, and concen- 

98. What substance transmits heat most readily? Which least so? 
What is rook-salt called ? 99. How is heat polarized, Ac ? 




trated, like light, and doubly refracting minerals; like Ice* 
land-spar, will polarize it. 

Expansion of Bodies by HeaL 

100. All bodies expand with an increase of hoat, and 
diminish with its loss. The expansion of a solid may be 
shown by a bar of metal which, as in 
the fig. 85, is provided with a handle, 
which at ordinary temperatures ex- 
actly fits the gauge. On heating this 
over a spirit-lamp, or by plunging it 
into hot water, it will be so much 
expanded in all its dimensions as no 
longer to enter the gauge. On cool- 
ing it with ice, it will again not only 
enter freely, but with room to spare. 
The same fact is shown by a ball, to 
which, when cold, a ring with a han- 
dle will exactly fit; but on heating Fig. 85. 
the ball, the ring will no longer encircle it. 

The expansion of & fluid may be shown by filling the bulb* 
of a large tube (fig. $6) with coloured water to a mark on 
the stem. On plunging the bulb into 
hot water, the fluid is seen to rise rapidly 
in the stem. If it be cooled by a mix- 
ture of ice and water, it is seen to sink 
considerably below the line. A similar 
bulb (fig. 87) filled with air, and hav- 
ing its lower end under water, is ar- 
ranged as in the figure, to show the ' 
expansion of air by heat. The warmth 
of the hand applied to the naked ball 
will be sufficient to cause bubbles of air 
to escape from the open end through! 
the water ; and on removing the hand, 
the contraction of the air in the ball, Fi * *•• Fi «* 8r - 

from the cooling of the surface, will cause a rise of the fluid 
in the stem, corresponding to the volume of air expelled, as 

100. What if expansion t niuitrate it for a solid. For a liquid. Fo* 
a gas. 





shown in the figure. The slightest change of temperature 
will cause this column of fluid to move, as the air expands 
or contracts. In fact, it is the old air-thermometer. 

101. Expansion of Solids. — Expansion by 'heat varies 
greatly: 1. According to the nature of the substance ; and, 
2. Not in degree only, but also in the law which it follows. 
In solids, between the freezing and boiling of water, the rate 
of expansion in the same solid is equal for each additional 
degree. In experiments on this subject, rods of equal length 
are used, composed of the various subjects of experiment, 
whose expansion in length is accurately measured. 

In fig. 88, the 
rod t is confined 
by a, so that its 
free end bears 
against b. Heat- 
ed by an alcohol 
lamp, or other 
source of heat, it 
!_ expands and car- 
ries forward the 
Fig. ss. index g over the 

graduated arc c. On cooling, it contracts, and the spring a 
moves the index back again to the starting point. This 
linear expansion, multiplied by 3, gives the expansion in 
volume very nearly. Thus, for example, in the following 
solids, when heated from 32° to 212° Fahrenheit, the ex- 
pansion is — 

In Length. 

In Bulk. 

339 parts of zinc 

















white glass 

black marble 

340 or 112 parts — 113 

— 350 « 116 

— 524 « 174 

— 584' 

— 644 

— 811 

— 922 
= 1007 

1114 " 371 
= 2832 « 

« 194 

" 217 

" 270 

" 307 

" 335 


— 117 

" — 175 

" ^=195 

« =-218 

« —271 

" — 308 

" —336 

" —372 

" —944 

102. The expansion of fluids is ether apparent or absolute, 
according as the dilatation of the containing vessel is or is not 

101. What is the rate of expansion in solids ? Describe fig. 88. Gire 
•samples from table, in length and bulk. 





taken into account. This fact may be m* 
illustrated in the annexed apparatus, (fig. 
89,) where a tube of glass is bent twice at 
right angles, the open ends a and b upper- 
most; a larger tube surrounds each, leaving 
two cells, in which water of different tem- 
peratures may be poured. The inner tube 
is filled, for example, with colored water, 
of the ordinary temperature, to the level P; 
hot water is now poured into the outer cell 
of bj when an immediate elevation of level 
in the colored fluid is seen to m. This is 
on the principle that the heights of columns 
of liquids in equilibrium are inverse to their 
densities. In this manner it has been de- 
termined that in heating from 33° to 212°, 
9 measures of alcohol becomes 10 ; of water, 
23 measures becomes 24 ; and of mercury, Flg * 89# 
55 measures becomes 56. Thus it happens that in the com- 
mon changes of the seasons the bulk of spirits varies about 
5 per centum. It has been determined, also, that liquids 
are progressively more expansible at higher than at lower 
temperatures. The liquefied gases illustrate this law in a 
remarkable manner, for fluid carbonic acid, as observed by 
M. Thilorier, has a dilatation four times greater than is ob- 
served in common air at the same temperatures. The law 
of expansion in liquids is not yet well made out. 

103. Unequal Expansion of Water. — The general law of 
expansion for nearly all solids and fluids, especially within 
the limits of the freezing and boiling points of water, is, 
that each solid or fluid expands, or contracts, an equal amount 
for every like increase, and reduction of, temperature, each 
body having its own rate of dilatation. There are, how- 
ever, some exceptions to this law, of which water offers a 
remarkable example. As the comfort, and even habitability 
of our globe, are in a great degree dependent on this excep- 
tion to the ordinary laws of nature, it is worthy of special 

If we fill a large thermometer-tube or bulbed glass (fig. 90) 
with water, and place it in a freezing mixture, where wo 

102. Describe the apparatus fig. 89. What is the expansion of water? 
Of alcohol ? 103. What inequality in the expansion of water ? 



72 HEAT. 

can observe the fall of the temperature by tin 
thermometer, we shall see the column descend 
A regularly with the temperature, until it reaches* 

11 39*°1 F., when the contrary effect will take place: 

|| the water then begins suddenly to rise in the tube, 

|| by a regular expansion, until the temperature 

—II — falls to 32°, when so sudden a dilatation takes 
I place as to throw the water in a jet from the open 

I orifice. If, on the other hand, we heat water in 

^L such an apparatus, commencing at 32°, we shall 

M^ find that, until the temperature rises to 40°, the 
^^r fluid, in place of expanding as we might expect, 

Kg. 90. will actually contract Water has, therefore, 
its greatest density at 39°-5, and its density is 
the same for equal temperatures above and below this point; 
thus we shall find it having a similar density at 34° and 45°. 
104. Beneficial Result*. — Let us now observe what useful 
end this curious irregularity in the expansion of water sub- 
serves. When winter approaches, the lakes and rivers, by 
the contact of the cold air, begin to lose their heat on the 
surface; the colder water, being more dense, falls to the bot- 
tom, and its place is supplied by warmer water rising from 
below. A system of circulation is thus set in motion, and 
its tendency, if the mass of water is not too large, is to reduce 
the whole gradually to the same temperature throughout. 
When, however, the water has cooled to 39 0, 5, this circula- 
tion is arrested by the operation of the law just explained : 
below this point the water no longer contracts by cooling, 
and of course does not sink; but on the contrary expanding, 
as before explained, it becomes relatively lighter, and remains 
on the surface : the temperature of this layer or upper stratum 
gradually falls, until the freezing point is reached, and a 
film of ice is formed. But as ice is a very bad conductor, 
the heat now escapes with extreme slowness; all currents 
tending to convey away the cooler parts of the water are 
arrested, and the thickness of the ice can increase only by 
the slow conduction through the film already formed : the 
consequence is, that our most severe winters fail to make ice 
of any great thickness. Other causes, also, which we shall 

What is its maximum density ? 104. What beneficial result follows ? 
Why is freezing a flow process ? Describe the mode of freezJbg of lakes 
and rivers. 




presently explain, co-operate at all times to render the freez- 
ing of water a very slow process. We cannot fail to be im- 
pressed by the wisdom of that Power, which not only frames 
great general laws for the government of matter, but also 
makes exceptions to them, when the welfare of His creatures 
requires them. 

105. The expansion of all gate* and vapours is the same 
for an equal degree of heat, and equal increments of heat 
produce equal amounts of expansion. The rate of expansion 
amounts to 7 ^th part of the volume of the gas at Q for 
each degree of Fahrenheit's scale, or between 32° and 212° 
to 0*366, or more than i of the initial volume of the gas. 

When gases are near the point of compression at which 
they become liquid, this law becomes irregular, and is not 
strictly true for all gases ; but the departures from the law 
are so small that we need not mention them here. 

106. Practical application of the laws of expansion in 
solids are frequently made with great advantage in the arts. 
The rivets which hold together the plates of iron in steam- 
boilers are put in and secured while red-hot, and on cooling 
draw together the opposite edges of the plates with great 
power. The wheelwright secures the parts of a carriage- 
wheel by a red-hot tire, or belt of iron, which being quickly 
quenched, before it chars the wood, binds the whole fabric 
together with wonderful firmness. The walls of the Con- 
servatory of Arts, in Paris, after they had bulged badly, were 
safely drawn into a vertical position, by the alternate con- 
traction and expansion of large rods of iron passed across it, 
and so secured by screw-nuts and heated by Argand lamps 
as to draw the walls inward. Towers of churches and other 
buildings have been thrown down or otherwise injured by 
the expansion of large iron rods (anchors) built into the 
masonry with the design of strengthening them. The Bun- 
ker Hill monument is daily bent out of a perfect vertical 
by the heat of the sun expanding the granite of which it 
is built. The mechanical arts are, in fact, full of beautiful 
applications of the principles of expansion. Among these 
we may mention 

107. The Compensation Pendulum, adapted to regulating 
the rate of time-pieces. The length of the pendulum is 

106. What is the law of expansion in gases ? How muoh does air dilate 
for each degree ? 106. Mention some instances of expansion in the arte* 





altered by variations of temperature, and of course the rata 
of the clock is disturbed. A perfect compensation for this 
error is obtained by the use of a compound 
pendulum of brass and iron, or other two 
metals, arranged as is shown in fig. 92, in 
such a manner that the expansion of one 
metal downward will exactly counteract that 
of the other metal upward; thus koeping 
the ball of the pendulum at a uniform dis- 
tance from the point of suspension. The 
shaded bars represent the iron, and the light 
ones the brass. The same object is accom- 
plished by using mercury, as shown in fig. 
91, contained in a glass or steel vessel at the 
end of the pendulum-rod. The expansion 
which lengthens the rod also increases the 
m volume of the mercury; this increase of bulk 
J) in the mercury raises the centre of gravity to 
jtt £_J an exactly compensating amount, and the 
Fig. 91. F^92 c * oc k rema i n s unaltered in rate. Watches and 
' chronometers are regulated by a like beautiful 
contrivance. The balance-wheel, (fig. 93,) on whose uniform 
motion the regularity of the watch or chronometer depends, 
is liable to a change of dimensions from 
heat or cold. If made smaller, it will 
move faster, and if larger, slower. To 
/^ ^\ avoid this error, the outside of the wheel 
IV" vl/" - ji is made of brass, the inside of steel, and 

vW ffl cut afc two °PP 0S * te P omt 8 ; one end of 

^^. ^^ each part is screwed to the arm, and the 
^^^■^^^ loose ends of the rim, being united by a 
Fig. 93. screw, are drawn in or thrown out by 

the changes of temperature, in precise proportion to the 
amount of change ; thus perfectly adapting the revolution 
of the wheel to the force of the spring. The principle of 
this wheel, it will be seen, is the same as in the compound 
bars, (107.) A pendulum of pine-wood is sometimes em- 
ployed for clocks, because it is so little changed by varia- 
tions of temperature. 

108. The unequal expansion of solids is well shown by 

107. What is the compensation pendulum? What the mercurial? 
What is the compensation balance ? 





joining firmly, by rivets, two bars, one of iron and one of 

brass, as in fig. 94. When 
they are heated, the brass 
expanding most, will canse 
the compound bar to bend, 
as shown in the fig. 95. 
If they are cooled by ice, 
the brass contracting most, 


Fig. 94. 

Kg. 95. 

will bend the united metals in an opposite direction, 

The Thermometer. 

109. The Thermometer is an instrument for measuring 
heat by the expansion of various liquids and solids. This in- 
strument was invented by Sanctorio, an Italian, in A. d. 1590. 
His was an air-thermometer, such as is figured in the context. 
A bulb of glass with a long stem is placid with its 
mouth downward, in a vessel containing a portion 
of colored water, (fig. 96.) A part of the air 
being first expelled from the ball by expansion, the 
fluid rises to a convenient point in the stem, to which 
is attached a scale of equal parts, with degrees or 
divisions marked by some arbitrary rule. Thus 
arranged, the instrument indicates with great deli- 
cacy any limited change of temperature in the sur- 
rounding air. The portion of air confined in the 
ball, when heated, expands, and pressing on the 
column of fluid in the stem, drives it down, accord- 
ing to the amount of expansion or the degree of 
heat; and the reverse results from a decrease of 
temperature. The air thermometer has given place to Fl *' 96, 

110. The Common Thermometer. — This instrument indi- 
cates changes of temperature by the expansion of mercury or 
of alcohol contained in the bulb blown upon the end of a very 
fine glass tube. Mercury possesses very remarkable properties 
fitting it for a thermometric fluid : it may easily be obtained 
pure ; its rate of expansion is singularly uniform between 
its boiling and freezing points, and the range of temperature 
between these points is greater than in any other fluid, (about 
660° Fahr.) For very low temperatures alcohol is preferred, 
as it has never yet been solidified, even with the intensest 

108. Describe figs. 94 and 95. 109. What is the thermometer? De- 
scribe Sanotorio's thermometer. 110. Describe the common thermometer. 





artificial cold of the carbonic acid bath (§151,) or of the arctic 
regions. The precautions needed to make a thermometer, 
such as will meet the demands of modern science, are too 
numerous to be fully described here. Suffice it to say, that 
by expanding the air in the empty ball, while the open end 
of the tube is covered with mercury, a portion of it is carried 
in by the pressure of the atmosphere, and by boiling this, 
. all air is expelled and the tube entirely filled 



9 a 


Fig. 97. 

£ with mercury. The quantity is so adjusted 
by trial that it will stand at a convenient 
height in the tube. Finally, the tube is sealed 
by the lamp, while the contained mercury is 
expanded to completely fill it. The empty 
space in a good thermometer is therefore a 
torricellian vacuum. 

111. Graduation of Thermometers. — The 
scales adapted to the thermometer in various 
countries are divided into arbitrary degrees, 
and, unfortunately for science, the scales differ 
widely. There are, however, two fixed points 
in all, which are determined by direct ex- 

J periment. These are the boiling and freezing 
points of water, or, more accurately, the melt- 
ing point of ice. The space between these 
- 1^: two points is divided into a certain number 

: of equal parts, according to the scale to be 
; : employed. In France, and on the continent 
of Europe generally, the scale of Celsius, or 
Centigrade, is employed, which divides this 
space into 100 degrees. In England and 
£j America the scale of Fahrenheit, a Hollan- 
der, is adopted. This scale adopts for its 

: zero point the cold produced by a freezing 
mixture of snow and salt; which its author 
assumed to be the greatest possible cold. The 
word zero signifies nothing, but we know that 
as cold is the mere absence of heat, it is hope- 
less to expect an absolute zero. The scale 
: ij±: of Reaumur, adopting the melting of ice as 

: zero, divides the space between that point and 
the boiling of water into 80 degrees. The 

111. How are thermometers graduated ? What are fixed points ? 




scale of De Lisle, which is no longer used, read downward 
from zero at boiling water to 150°, the freezing of the same. 
Annexed, in fig. 97, we have these four scales compared. It 
will be seen that zero Centigrade is zero Reaumur and 32° 
Fahrenheit; while 100° ,C. = 80° R. =212° F. In other 
words, these three scales divide the space between the two 
fixed points respectively into 100° C, 80° R., and 180° F. ; or, 
reducing to smallest terms, 5° C. = 4° R .= 9° F. To reduce 
Centigrade to Fahrenheit, we can multiply by 9 and divide 
by 5, and add 32° to the quotient, and vice versa. Suppose 
we wish to know what 70° C. is on Fahrenheit's scale; we 
have the proportion 5 : 9 : : 70° : 126°. If we add 32°, which 
is the difference between zero of F. and C, we have 126° + 
82° = 158°, which is the number required, for 70° C. = 
158° F. In stating thermometrical degrees, the sign + i* 
used for points above zero, and — for those below. Fahren- 
heit's scale is the one employed in this work. 

112. The SfUf'Registering Thermometer is a form of the 
instrument contrived for the purpose of ascertaining the 
extremes of variations which may occur, as, for instance, 
during the night. It consists of two horizontal thermometers 
attached to one frame, as in fig. 98 ; 6 is a mercurial ther- 


mometer, and measures the maximum temperature, by push- 
ing forward, with the expansion of the column, a short piece 
of steel wire, of such size as to move easily in the bore of 
the tube ; it is left by the mercury at the remotest point 
reached by the expansion ; a is a spirit-of-wine thermometer, 
and measures the minimum temperature. It contains a short 
cylinder of porcelain, shown in the figure, which retires with 
the alcohol on the contraction of the column of fluid, but 
does not advance on its expansion. 

Name the three scales. What is boiling water in each ? What freez- 
ing? Convert Centigrade 70° to Fahrenheit 112. What is the self- 
registering thermometer ? 





113. The Differential Thermometer is a form of air-ther- 
mometer, so named because it denotes only differences of 

temperature. It consists of two bulbs 
on one tube, bent twice at right angle% 
and supported, as shown in fig. 99. A 
little sulphuric acid, water, or other 
fluid partly fills the stem only. When 
the bulbs of this instrument are heated 
or cooled alike, no change is seen in the 
position of the column ; but the instant 
any inequality of temperature exists 
between them, as from the bringing the 
hand near one of them, the column of 
Fig. 99. fluid moves rapidly oyer the scale. A 

modification of this instrument, of great delicacy, was con- 
trived by Dr. Howard of Baltimore, in which sulphuric ether 
was the fluid used, the bulbs being vacuous of air. 

114. A Pyrometer is an instrument for measuring high 
temperatures. As mercury boils at about 660°, we can 
estimate the temperature of fused metals, and the like, only 
by the expansion of solids. The only instrument of this 
sort which we need mention, as it is the only one susceptible 
of accuracy, is Daniell's Register Pyrometer. It consists of 
a hollow case of black-lead, or plumbago, into which is 
dropped a bar of platinum, secured to its place by a strap 
of platinum and a wedge of porcelain. The whole is then 
heated, as, for instance, by placing it in a pot of molten silver, 

whose temperature we wish to 
ascertain. The metal bar expands 
pi cj ^^B much more than the case of black- 

lead, and being confined from 
moving in any but an upward 
direction, drives forward the arm 
of a lever, as shown in fig. 100, 
over a graduated arc, on which 
we read the degrees of Fahren- 
heit's scale : (this graduation has 
been determined beforehand with 
great care.) This instrument 
gives very accurate results; by 
Fig. 100. it the melting point of cast iron 

113. What the differential? 114. What are pyrometer*? 





baa been found to be 2786° R, and of silver 1860° F. 
The highest heat of a good wind-furnace is probably not 
much above 3300°. Fig. 88 (101) is a pyrometer of ordi- 
nary construction. 

115. Breguet* thermometer is constructed 
upon the principle of the unequal expansion 
of metals, (107.) A compound piece of me- 
tal is formed by soldering together two equal 
masses of silver and platina — two metals 
whose expansion is very unequal. This is _ 
rolled thin and coiled into a spiral as shown K 101> 
in a 6, (fig. 101.) It is suspended from a 
fixed point p 9 while its lower end is free and carries an 
index t. Variations of temperature cause this spiral to un- 
wind or wind up, and these motions are indicated by the 
motion of the pointer. This is a more delicate thermometer 
than any mercurial or spirit one. A beautiful modification 
of Breguet's thermometer has been contrived by Mr. Saxton, 
to measure the temperature of the sea in deep soundings. 

116. All thermometers for accurate research are divided 
on the glass stem by aid of a graduating engine and mi- 
crometer j each instrument being, according to the plan of 
Regnault, graduated by an arbitrary scale. 

Capacity for Heat, or Specific Heat 

117. Different bodies have different capacities for heat. 
If equal measures of mercury and of water, for example, 
are exposed to the same source of heat, the mercury will 
reach a given temperature more than twice as soon as the 
water, and it will cool again in half the time. Mercury is 
said, therefore, to have only half the capacity for heat which 
water has. We learn by trial that each substance in like 
manner has its own relations to heat as respects capacity. 
This is called also specific heat, a term synonymous with 
capacity. Water is adopted as the standard of comparison 
for this property, and the trial is usually made upon equal 
weights rather than upon equal measures of the substances 
compared. Specific heat connects itself curiously with the 
atomic constitution of matter. Several modes may be em- 

115. What is the metallic thermometer ? 116. How are thermometer! 
accurately graduated ? 117. What is capacity for heat ? Give exaioploi. 
What is specific heat? 





ployed to determine it; as by mixture, by melting, by 
warming, or by cooling. The determination of this property 
is called calorimetry, and the modes of experiment most 
usual are either by mixture or by the fusion of ice. 

118. The Method of Mixtures. — If a pint measure of 
water, at 150°, be mixed quickly with an equal measure of 
the same fluid at 50°, the two measures of fluid will have 
the temperature of 100°, or the arithmetical mean of the 
two temperatures before mixture. If, however, we rapidly 
mingle a measure of water at 150°, and an equal measure 
of mercury at 50, we shall find that they will have the tem- 
perature of 118°. The mercury has gained 68°, and the 
water lost about half as much, or only 32°. Hence we 
infer that the same quantity of heat can raise the tempera- 
ture of mercury through twice as many degrees as that of 
water, and that the specific heat of water will be to that 
of mercury as 1 : 047, when compared by measure. But 
if we divide this number (0-47) by the density of mercury 
(13*5) we obtain the number 0.035, which expresses the 
specific heat by a comparison of weights. Water has then 
more than 30 times the capacity for heat which is found in 
mercury ; and in this peculiarity we find an important rea- 
son of the singular fitness of this fluid metal for the con- 
struction of thermometers. 

119. By the melting of teem the calorimeter of Lavoisier, 
is in fig. 102, the capacity of most substances for heat has 
teen determined. A set of metallic vessels abc are so 

arranged that when a warm body is 
placed in c, all the heat it gives off in 
cooling will go to melt the lumps of ice 
surrounding it. The water of fusion 
escapes at the cock *, and is measured 
in the graduated glass beneath. To 
cut off the heat of the surrounding air, 
the space between a and b is also filled 
with ice. The water which melts from 
this portion is carried away by r. In 
this apparatus the relative capacities 
of all solid and fluid substances may, 
with proper precautions, be accurately 

Fig. 102. 

What is calorimetry? 118. Describe the method of mixtures. 119. 
What is Lavoisier's calorimeter ? 





determined by the respective measures of water which flow 
from s during the experiment, in which each body cools 
from an agreed temperature, (e. g. 212°) to 32°, the constant 
temperature of c. The same result may be reached in some 
cases more simply by employing a large lump 
of solid ice a (fig. 103) in which a weli W has 
been scooped out, and covered by a lid of ice 6. 
Any solid substance, or a fluid contained in a I 
glass flask, may be placed in W, and, when the | 
temperature has fallen to 32°, the water con- «. 10 « 
tained in W may be measured as before. To es- * s ' 
timate the capacity of heat in gases, atmospheric air it 
chosen as unity — and the method of melting is adopted by 
passing a certain volume of gas through a tube refrigerated 
by ice. 

120. It is plain, from what has been said, that the capar 
city of bodies for heat is a phenomenon not indicated by 
the thermometer. In the foregoing experiments, water and 
mercury have been each heated to 212°, and yet the result 
demonstrates that an equal weight of water contains at that 
temperature about 30 times as much heat as the mercury. 
The thermometer can indicate only actual intensity of heat, 
and not its volume or quantity. 

In the following table of specific heats, it will be seen 
that this property has much connection with the physical 
condition of bodies as respects fluidity or crystalline ar- 
rangements, as is evident by comparing the capacity of 
water and ice, and of the various forms of carbon : — 

Water 1000 

Ice 513 

Turpentine 468 

Carbon (charcoal) 241 

Anthracite (Pa.) 201 

Graphite... 201 

Diamond 146 

Btoel 116 

Sulphur 177 

Sulphur lately 

fused 184 

Ether 520 

Alcohol 660 

Mercury 33 

Iron 114 

Copper 95 

Zinc 95 

Brass 94 

Silver 57 

Antimony 51 

Gold ; 32 

Lead 31 

Phosphorus 118 

Glass W 

Changes produced by Heat in the State of Bodies. 

121. Fluidity is a result of temperature, as is seen in the 
familiar case of water, which is either ice, water, or steam, 

What simpler one is described ? 120. What docs the thermometer tail 
in indicating? Give examples from table. 121. What is fluidity ? 




82 HEAT. 

according to the temperature to which it is subjected. Many 
solids can be melted by an increase of temperature, and the 
melting point is always the same for a given solid. Some 
substances pass at once to the fluid state, while others, 
as wax, assume an intermediate pasty condition, and others, 
like ice, fuse very slowly indeed. The degree of heat at 
which bodies melt varies exceedingly. Thus platinum is 
not melted at 3280°. Iron melts at about 2800° ; gold, at 
2016°; silver, 1873° ; zinc, 773°; lead, 612°; tin, 442°; 
Newton's alloy, 212°; potassium, 136° ; phosphorus, 108°; 
wax, 142°; tallow, 92°; olive oil, 36°; ice, 32°; milk, 
30°; wines, 20°; mercury, —39°; fluid ammonia, —46° ; 
ether, — 47°; while pure alcohol is not solid at 175° below 
Fahrenheit's zero. 

122. Liquefaction is attended by a remarkable absorption 
of heat. We have already seen that two equal measures of 
water at different temperatures assume when mingled the 
mean of their previous temperatures, (118.) If, however, 
we take a pound of ice at 32°, and a pound of water at 
212°, we shall find, when the ice is melted, that the two 
pounds of water have the temperature of only 52° ; the ice 
gains only 20°, while the water has lost 160°. There are, 
then, 140° of heat lost in producing this change. We can 
take another mode of trial. Let us expose a pound of ice 
and a pound of water, each at 32°, to a constant source of 
heat, in two vessels every way alike, and note the changes 
of temperature by the thermometer. The same quantity 
of heat is flowing into each vessel. When the ice is all 
melted, we shall find that the water into which it is con- 
verted has still only the temperature of 32°, while the other 
pound of water has risen from 32° to 172° : here again we 
see the loss of 140° of heat used in converting the ice into 
water. We may reverse the last experiment, and take equal 
weights of ice at 32° and water at 172° and mix them : 
when the ice is all melted the mixture will still have the 
temperature of only 32° ; so that, in whatever way we may 
make the trial, we constantly observe the loss of 140° of 
heat. This is called the heat of fluidity y it being necessary 
to the existence of the water in a fluid state ; and it is also 
designated latent heat, because it is lost, absorbed, or con- 
Name the fluidity-points of several bodies. 122. What phenomenon 
attends liquefaction? Give an example. How is this reversed? What 
is latent heat ? 




eealed, as it were, and no indication of it can be found by 
the thermometer. 

123. This law is equally illustrated by the slow freezing 
of water. If a vessel filled with water at 52° be placed in 
an atmosphere of 32°, it will rapidly cool down to 32° by 
the losd of 20° of temperature. After this, it will, as may 
be seen by the thermometer, remain at 32°, until it is all 
converted to solid ice ; although we cannot doubt that it is 
all the while giving out a quantity of heat, which had before 
been insensible or latent. If the water had been ten 
minutes in cooling from 52° to 32°, (or in losing 20°,) 
then it would require one hour and ten minutes, or seven 
times as long, for it to become completely frozen. If, then, 
in equal times it lost equal degrees of heat, its latent heat 
will be 20° X 7 = 140°, which is the same result as 

Thus we arrive at the seeming paradox that freezing is a 
warming process. By experiment we may show that water 
may be cooled some 8 or 9 degrees below its freezing point 
and still remain liquid, if its surface be covered with a thin 
film of oil, or if it is a thin smooth vessel, kept quite still ; 
but the least disturbance will cause it, when in this situa- 
tion, to become solid at once, and the temperature will im- 
mediately rise from 23° or 24° to 32°. The freezing of a 
part has therefore given out heat enough to raise the tem- 
perature of the whole from 24° to 32°, or through 8°. Our 
domestic experience in cold climates often supplies examples 
of this fact. The solidification of a saturated solution of sul- 
phate of soda is also an example of the same nature ; the ves- 
sel containing the solution becomes sensibly warm. In like 
manner, it is true that melting is a cooling process. A solid 
can melt only by absorbing heat from surrounding bodies, 
which must, of course, become cooler. Hence, in part, the 
cooling influence of an iceberg, which is often felt for many 
leagues, or of a large body of snow on a distant mountain ; 
and the chill felt in the air on a bright day in spring, when 
snow is rapidly melting on the ground. 

It is a wise order of nature that makes the freezing and 
thawing of snow and ice extremely slow and gradual pro- 

123. Illustrate it by the freezing of water. How may water remain 
Kquid below 32° ? How is freezing a warming process ? What proof 
of design is here indicated? 



84 HEAT. 

cesses. If -water became solid at once on reaching 32°, it 
would be suddenly frozen to a great depth; and if ico 
melted as quickly on reaching the same temperature, the 
most sudden and dreadful floods would accompany these 
events, and the common changes of the seasons would bo 
calamitous to human comfort and life. 

124. Freezing mixtures owe their powers, to the principles 
just explained. Ice-cream is frozen by a mixture of snow 
or pounded ice with common salt. In this case, the two 
solids are rapidly changed to fluids ; the ice is melted by 
the sal^ and the salt is dissolved by the water from the 
melting ice. Both these operations absorb a large quantity 
of heat. The surrounding bodies are called on to supply the 
heat required, and the cream in a thin metallic vessel cools 
so rapidly as to be soon turned to ice. The thermometer 
will fall in this operation to 0° F. ; and this was the very 
experiment by which Fahrenheit (111) assumed that he had 
attained to a true zero of cold. 

Nitrate of ammonia dissolved in water at 46° will sink the 
temperature to zer"), and the exterior of the vessel becomes 
at once thickly covered with hoar-frost. Common saltpetre, 
(nitrate of potassa,) dissolved in water, lowers its tempera- 
ture about 15° or IS , and is therefore much used in the hot 
regions of Asia, where it abounds, for cooling wine. Mer- 
cury may be frozen by using a mixture of three parts of 
chlorid of calcium and two of dry snow ; this mixture will 
sink the temperature from -(-32 ° to — 50°. Five parts of 
finely-powdered sal ammoniac and five of nitre, dissolved in 
nineteen of water, will reduce the temperature from 50° to 
10° ; and a little powdered sulphate of soda, drenched with 
strong hydrochloric acid, will sink the thermometer from 50° 
to 0°. But the most intense cold is that which results 
from the volatilization of liquefied carbonic acid and nitrous 
oxyd gases, by which the enormously low temperatures of 
—175° and even 220° are reached. 

125. Diminution of volume causes a portion of latent 
heat to become sensible. Air suddenly compressed into a 
small space, as in the fire-syringe, (fig. 104,) evolves heat 
enough to fire a portion of dry punk on the end of the 
piston. Metals rapidly struck, as on an anvil, become hot 

124. What are freezing mixtures ? Give their theory. What if the 
tort intense artificial cold ? 125* What ignites tinder in the fire-syringe t 




enough to enable the smith to light his fire. Wa- 
ter poured on quicklime combines with it, with the 
evolution of much heat; the water in this case 
taking on the solid form. Sulphuric acid and 
water, when mingled, give out great heat, and the 
bulk of the mixture is less than that of the two 
before mixing. Liquefaction is always a cooling 
process, and solidification or condensation a heat- 
ing one. A certain quantity of heat may be con- Fig. 104. 
sidered as necessary to preserve each body in its 
natural condition : if it be condensed, less is required, and 
it gives out the excess ; and if expanded, it absorbs more. 

Vaporization. — The Boiling Pbints of Bodies. 

126. A continuance of the heat which melted the ice into 
water, will turn the water into vapor or steam. The phe- 
nomena which attend this physical change are not less curious 
or instructive than the last. 

If we place a known quantity of water over a steady source 
of heat, we shall see the thermometer indicating each mo- 
ment a higher temperature, until, at 212°, the fluid boils; 
after which the thermometer indicates no further change, 
but remains steady at the same point until all the water is 
boiled away. Let us suppose that, at the commencement of 
the experiment, the temperature of the water was 62°, and 
that it boiled in six minutes after it was first exposed to the 
heat : then the quantity of heat which entered into it each 
minute was 25°, because 212°, the boiling point, less 62°, 
leaves 150° of heat accumulated in six minutes, or 25° each 
minute. Now if the source of heat continue uniform, we 
shall find that in forty minutes all the water will be boiled 
away; and hence there must have passed into the water, to 
convert it into steam, 25° X 40 = 1000°. One thousand 
degrees of heat, therefore, have been absorbed in the process, 
and this constitutes the latent lieat of steam. So much heat, 
indeed, was imparted to the water, that if it had been a fixed 
solid, it would have been heated to redness; and yet the 
steam from it, and the fluid itself, had during the whole time 
a temperature of only 212°. 

125. Give examples of beat evolved from condensation. 126. What is 
Vaporization ? What is the latont heat of water ? How is it observed ? 



86 HEAT. 

127. The capacity of water for heat is greater than thai 
of any other body known; and in vapor it preserves the 
same distinction. The latent heat of steam has been vari- 
ously stated by different experimenters at 940°, 956°, 960°, 
972°, and 1000°. The latest, and probably the most accurate 
determination, is that of Brix, viz. 972°. The latent heat of 
vapors has no relation to their points of boiling. The supe- 
riority of vapor of water in respect to latent heat will be seen 
by a comparison with that of several other bodies, viz. latent 
heat of vapor of water = 972°, of ammonia 837°, of alcohol 
386°, of ether 162°, of oil turpentine 133°. The large amount 
of latent heat contained in steam becomes again sensible on 
its condensation to water ; thus enabling us to make great 
use of it as a means of conveying heat. The steam, so to 
speak, takes up a large quantity of heat, and transports it 
to the point where we wish it applied. One gallon of water 
converted into steam, at the ordinary pressure of the atmo- 
sphere, will raise five gallons and a half of ice-cold water 
to the boiling point. In this way we can boil water in 
wooden tanks, heat large buildings by steam-pipes, and make 
numberless other useful applications of steam-heat in the arts. 
It is found in practice that to heat buildings by steam, every 
2000 feet of space to be heated to 75° requires one cubic 
foot of boiler capacity, and that every square foot of radiat- 
ing surface on the conducting pipes will heat 200 cubic feet 
of space. 

128. The boiling point of each fluid is constant, other 
things being equal, but is peculiar to itself; thus, ether boils 
at 96°, ammonia at 140°, alcohol at 173°, water at 212°, 
nitric acid 250°, oil turpentine 314°, phosphorus 554°, sul- 
phuric acid 620°, whale-oil 630°, and mercury at 662°. 

129. Boiling is the mechanical agitation of a fluid by its 
own vapor. This happens whenever the liquid becomes so 
hot that its vapor can rise in bubbles to the surface, uncon- 
demnned by atmospheric pressure or by the temperature of 
the fluid. * The elasticity or tension of the vapor then bo- 
comes greater than the united pressure of the fluid and the 
air. When the boiling is vigorous, a great number of these 
bubbles of uncondensed vapor rise to the surface at the same 

127. What capacity has water for heat ? Give other latent beats. Why 
♦he superiority of water for steam purposes ? 128. What of the boiling 
points of fluids ? 129. What is boiling ? 





instant, and the liquid is thrown into violent agitation. If 
a vessel containing cold water be heated suddenly, the lowei 
surface receives the most heat ; bubbles of vapor are formed, 
and rise a little way, when, meeting the colder water, the 
vapor is at once condensed, and the liquid, before sustained 
by the elastic vapor, falls with a blow on the bottom of the 
vessel, often destroying it, if of glass. 

130. The boiling point is much affected by the nature 
and condition of the vessel. In a metallic vessel, water boils 
at 210° and 211°. If a glass vessel be coated inside with shel- 
lac, water boils in it at 211° ; but if it be thoroughly cleaned 
with sulphuric acid, water in it may be heated to 221° or more, 
without the escape of bubbles. A few grains of sand, a little 
fragment of wire, or a small piece of charcoal will, however, 
at once equalize these differences, and cause the water to 
boil steadily at 212°. This simple means will prevent the 
unpleasant jar from sudden escape of vapor, and frequent 
fracture of the glass vessel. The boiling point is more re- 
markably affected by variations in atmospheric pressure than 
by any other cause, and we shall presently advert more in 
detail to the phenomena connected with it. 

131. Spheroidal State of Liquids. — If drops of water are 
let fall on a metallic plate heated considerably above the 
boiling point, it is observed that they do not 
evaporate very rapidly, and that there is no hiss- T 
ing sound, while the globules of water roll ' 
about quietly, floating, as it were, over the hot 
surface. Thus situated, water is said to be in 
the " spheroidal state/' a term employed by M. 
Boutigny, who has made many curious and in- 
structive experiments on this subject. Water 
passes into this condition at 340°, and may at- 
tain it even at 288°. A grain and a half of water 
in this state at 392° requires 3*30 minutes to 
evaporate; at a dull red-heat, the same quantity 
will last 1 -13 minutes, and at a bright red, 0*50, 
the rate of evaporation increasing with the tem- 
perature. The water, in these experiments, 
does not touch or wet the hot surface, but is- 
kept at a sensible distance from it by the elas- **«• 105 - 

136. What affects the boiling point? 131. What is the spheroidal 
state ? Describe the experiment in fig. 105. 





tic force of an atmosphere of its own vapor, as well also as 
by the repulsive action of hot surfaces. The vapor is a 
nonconductor, and its formation abstracts the sensible heat 
from the fluid ; so that, notwithstanding the proximity of 
the red-hot metal, the temperature of the fluid is found to be 
always lower than its boiling point, being, for water, 205°-7; 
for alcohol, 168° ; for ether, 93°-6 ; for hydrochloric ether, 
50 o< 9, and for sulphurous acid 13°1. The temperature is 
estimated as shown in fig. 105, where the liquid is contained 
in a metallic capsule in the flame of a good eolipile. 

132. If a thick and heavy silver capsule is heated to full 
whiteness over the eolipile, it may by an 
adroit movement be filled entirely with wa- 
ter, and set upon a stand, some seconds 
before the heat declines to the point when 
contact can occur between the liquid and the 
metal. When this happens, the water, be- 
fore quiet, bursts into steam with almost 

explosive violence, and is projected in all 

directions, as shown in fig. 106. 

On the principle explained, the hand may be bathed in a 

vase of molten iron, or passed through a stream of melted 

metal unharmed ; and we find here an explanation of the 

success of some instances of magic. 

133. The pressure of the atmosphere determines the boiling 
point of fluids. It follows, therefore, that by a di- 
minution of pressure, water may be made to boil 
at a much lower temperature than 212°. If we 
place some warm water in a glass under the air- 
pump bell (fig. 107) and exhaust the air, the water 
will boil vigorously, although the temperature, as 
noted by the thermometer, is observed to fall con- 
stantly. So, in ascending high mountains, the 

boiling point falls with the elevation, from the diminished 
pressure of the air. On this account, a difficulty is expe- 
rienced at the hospice of Saint Bernard, on the Swiss Alps, 
in cooking eggs and other viands in boiling water. This 
place is 8400 feet above the sea, and water boils there at 
196° : on the summit of Mount Blanc, it boils at 184°. Wc 

Fig. 107. 

132. Describe fig. 106. Why can the hand be safely plunged in fluid 
iron ? 133. What determines the boiling point of fluids ? How is it o* 
high mountains ? 





learn that it is the temperature, and not the boiling which 

Serforms the cooking. The Rev. Dr. Wollaston proposed to 
etermine the height of mountains by the boiling point. He 
found an ascent of 530 feet to be equal to a decrease of 1° 
in the boiling point ; and with a thermometer having large 
spaces considerable accuracy may be attained. In deep pits 
(as in mines) the boiling point rises. 

134. The culinary paradox gives a very good illustration 
of the phenomena of boiling under diminished pressure. A 
small quantity of water is boiled in a glass vessel, as in the 
figure : when the water is actively boiling, a good cork is 
firmly inserted, and the vessel removed from the heat. It 
may now be supported in an inverted position, with the 
mouth under water, as seen in the figure. The boiling will 
still continue, even more rapidly than before ; and if we at- 
tempt to check it by affusion of cold water, we shall only 
cause it to boil more vehemently. A little hot water will, 
however, at once arrest the ebullition. In this case, the air 
is driven out of the vessel on the first boiling of the water; 
and, as we close the orifice while the steam is still issuing, 
there is only the vapor of water in the cavity. 
As this condenses from cooling, the pressure 
on the water diminishes, and it boils more 
easily from the heat it still contains: the affu- 
sion of cold water, by producing a more per- 
fect condensation, occasions a more violent 
ebullition. Hot water, however, increases the 
elasticity of the uncondensed vapor, and re- 
presses the boiling. These alternations can 
be produced as long as the water in the vessel 
is warmer than the cold water poured on it. 
When cold, the space. over the water will be a 
good vacuum, and if we turn the water from 
the ball into the neck, it will fall like a solid 
body, with a smart blow and rattling sound. 
This is sometimes called the ivater-hammer. 
The perfection of the vacuum can be tested 
by withdrawing the cork under water : the 
pressure of the atmosphere will then drive in Flg ' 108, 
a quantity of water equal to the vacuum produced by the 
first expulsion of the air. 

134. What is the culinary paradox ? Explain the continued boiling. 



90 HEAT. 

135. The Puhe Glass of Dr. 

Franklin is a very good illustration, 

p. im also, of boiling under diminished 

lg ' ' pressure ; and the cool sensation felt 

by the hand at the instant when the fluid boils most violently, 

is proof of the heat absorbed in converting a part of the 

fluid into vapor. 

Practical application of these facts is made in the arts on 
a large scale, as in manufacturing sugar. The boiling of 
the syrup is performed in vacuo, in large pans of copper, 
holding 'several hundred gallons, the air and vapor being 
removed from the vessels by the air-pump of a steam-engine : 
the syrup is thus rapidly boiled down at a temperature of 
150° to 180°, without any danger of burning. Vegetable 
extracts are frequently made, and saline solutions boiled, in 
the same way. Nothing in the arts shows more clearly the 
value and beauty of scientific principles. 

136. Ehvation of the Boiling Point by Pressure. — In 
Papin's digester, (fig. 110,) a strong iron vessel with a safety- 
valve, water may be heated under the pres- 
sure of its own vapor to 400°, or higher. 
This apparatus may be so arranged with a 
thermometer and pressure gauge, (fig. Ill,) 
that we can note the relations of pressure and 
temperature (Marcet's apparatus) : the ther- 
mometer-ball is in the steam cavity; the 
gauge descends into some mercury in the 
bottom. It is supported by a tripod / over 
a lamp e, and a stopcock d cuts off the ex- 
Fig. 110. ternal air, when the boiling has commenced. 
As the steam accumulates, it, pressing on the mercury, forces 
it up the tube, against the imprisoned air in the gauge b. 
When the gauge shows double the pressure of the air, the 
thermometer will indicate a temperature of 250°*5. 3 at- 
mospheres of pressure raise the temperature to 275°, 4 to 
293°-7, 5 to 307°, 10 to 358°, 15 to 392°-5, 20 to 418°-5, 
25 to 439°, 30 to 457°, 40 to 486°, and 50 atmospheres 
raise it to 510^. Perkins heated steam so highly that a 
jet of it set fire to combustible bodies. 

135. Explain the pulse-glass. What practical application is made of 
these principles? 136. What is Papin's digester? What Marcet's? 
What relation is there between boiling points and pressure ? 





The clastic power of steam in con- 
tact with water is limited only by 
the strength of the containing ves- 
sel ; bat if steam alone be heated 
without water, then its elastic or 
expansive power is exactly like that 
of other gases or vapors. M. de la 
Tour has shown that many liquids 
may be entirely converted into va- 
por in a space but little greater than 
their own volume. 

137. The increase of volume in 
changing from a liquid to a gaseous 
state is such, that 1 cubic foot of 
water becomes nearly 1700 cubic 
feet of steam; or, in whole num- 
bers, a cubic inch of water becomes 
nearly a cubic foot of steam ; while 
1 cubic foot of alcohol and ether 
yield respectively 493 and 212 cubic 
feet of vapor. The latent heat of 
steam diminishes as the sensible 
heat rises, so that the heating power 
of steam at 400° is no greater than 
that of an equal volume at 212°. 
On the other hand, the latent heat 
of steam produced at low tempera- 
tures, as in a partial vacuum, in- 
creases as the sensible heat falls. 
Hence there is no fuel saved by dis- 
tilling in vacuo. There is a con- 
stant ratio between the latent and 
sensible heat of steam ; the two added together always give 
the same sum. Thus, steam at 212° has latent heat = 972°; 
giving the sum 1184°. Subtract the sensible heat of steam 
at any temperature from the constant number 1184, and we 
have the latent heat for that temperature, e. g. steam at 
280° has a latent heat of 904°. So, also, at 100°, steam 
has 1084° of latent heat. 

138. Equal volumes of different vapors contain equal quan- 
tities of latent heat. By weight, water vapor has about twice 

Fig. ill. 

What was De la Tour's observation? 137. What is the dilatation of 
■team ? What relation between oensihlo and latent heat ? 





Fig. 112. 

and a half more latent heat than alcohol vapor, (972 : 885;) 

but tho specific gravity of alcohol vapor is about 2*5 times 

*L greater than that of water-vapor, (1590 : 622.) 

1 Consequently, if the same expenditure of heat 

I produces from all vapors the same bulk of 

II vapor having equal quantities of latent heat, 
J-i there can be no advantage in substituting any 

^^ other fluid for water as a source of vapor in 

the steam-engine. 

139. The Steam-Engine. — The principle 
of this apparatus is simple, and easily illus- 
trated by the little instrument contrived by 
Dr. Wollaston, (fig. 112.) A glass tube, with 
a bulb to hold a little water, is fitted with a 
piston. A hole passes from the under side 
through the rod, and is closed by a screw at a. 
This screw is loosened to admit the escape of 

J the air, and the water is boiled 

over a lamp : as soon as the steam 
issues freely from the open end of 
the rod, the screw is tightened, 
and the pressure of the steam then 
raises the piston to the top of the 
tube ; the experimenter withdraws 
it from the lamp, the steam is 
condensed, and the air pressing 
freely on the top of the piston 
forces it down again; when the 
operation may be repeated by again 
bringing it over the lamp. 

In the common condensing en- 
gine (fig. 113) a cylinder a is 
fitted with a solid piston, the rod 
of which moves through a tight 
*~l packing in the cover, and to it the 
machinery is attached. A pipe 
d brings the steam from a boiler 
to the valve arrangement c by 
which the steam is admitted, alter- 
nately, to the top and bottom of 

Fig. 113. 

138. What of equal volumes of different vapors ? Compare alcohol 
and water. 139. What is Wollaston's toy? Give the principle of thf 
Bteam-cngine in fig. 112. 





the cylinder ; and also an alternate communication is opened 
with the condenser b. Thus, when the steam enters at the 
top, (in the direction of the arrow,) that at the bottom of 
the piston is driven through the lower opening to b, where 
it is condensed. The valves are moved at the proper time 
by the machinery. 

140. Evaporation from the surface of liquids takes place 
at all temperatures. Even snow and ice waste by evapora 
tion, at temperatures much below 32°. Mercury rises in 
vapor even at the temperature of 60°. Faraday found at 
that temperature that a slip of gold-leaf suspended in a 
vacuum over mercury was, in a few hours, whitened by amal- 
gamation with the vapor of that metal. The state of the 
atmosphere as to dryness and pressure influences 
natural evaporation, which is greatly increased by 
heat and a rapid wind. It must be remembered 
that all the water which falls to the earth in snow 
and rain has arisen in evaporation. That natural 
evaporation takes place only from the surface is 
proved, by its being entirely prevented by. a film 
of oil on the fluid. 

141. Influence of Pressure on Evaporation. — If 
we introduce a few drops of water into the vacuum 
above the mercury in a barometer tube, a part of 
it will be vaporized, and the level of the mer- 
cury will be correspondingly reduced. The tension 
of the vapor is increased by an elevation of tem- 
perature. A larger tube may be placed over the 
barometer tube, the lower end of which dips under 
the mercury, and we may then fill the intervening 
space with hot water, ffig. 114.) The vapor of 
the confined water will force down the column of 
mercury in direct proportion to the temperature ; 
and, by means of a thermometer and a scale of 
inches, we can tell exactly the tension of the vapor 
of water for every temperature under 212°. 

142. Maximum Density of Vapors. — Into the 
torricellian vacuum introduce a portion of sulphuric 
ether: a part of it is instantly converted into 
vapor, and the mercury depressed thereby to lfr 

140. What of natural evaporation? 141. What influence has present* 
on evaporation? 





about 14 inches. If we have a deep cistern, as in fig. 115, 
in which we can depress the tube by the pressure of the 
hand, it will be seen that the film of liquid 
I on the surface of the mercury increases as the 
tube descends, until the vapor of ether is 
at last entirely converted to the fluid state. 
On withdrawing the hand, the ether again 
flashes into vapor. There is then, it is plain, 
a point of density (or pressure) for the vapor 
of ether, which cannot be passed without again 
converting it to a liquid. This is true of all 
volatile liquids ; and this point is called the 
maximum density of vapors. The weight 
of 100 cubic inches of water vapor at 212° is 
14*962 grains, while, at 32°, the same volume 
of vapor of water is only 0-136. The point 
of maximum density of a vapor is lowered by 
cold as well as by pressure, and when these 
two effects are united, we can convert many 
gases, which are quite permanent at the com- 
mon pressure and temperature of the air, into 
liquids, and even to solids. 

143. The cold produced by evaporation is 
owing to the assumption of heat by the newly 
formed vapor. Availing ourselves of this prin- 
ciple, water may be frozen by the evaporation 
of ether, even in the open air. Leslie showed 
that water might be frozen by its own evapo- 
ration, as in the experiment figured in the mar- 
gin, (fig. 116.) Water is contained in a shal- 
low capsule supported by a tripod of wire 
over a dish containing sulphuric acid, and 
the whole is covered by a low air-jar. On 
working the pump, the water eva- 
porates so rapidly in the vacuum 
as to boil even at 72° : its vapor 
is instantly absorbed by the sul- 
phuric acid, and in this way both 
Fig. 116. the sensible and latent heat are 

removed so rapidly that the water is frozen, while still ap- 
parently boiling. 

142. What is meant by maximum donsity of vapors ? 143. Whence 
the cold of evaporation '( What is Leslie's experiment? 

Fig. 115. 




The Cryophorus, or frost-bearer, offers another illustration 
of the same principles. This instrument, invented by Dr. 
Wollaston, consists of two glass bulbs blown upon the same 
one of them 
contains a lit- 
tle water; the 
space over the 

water is a va- Fi £- lir * 

cuum, the tube having been sealed when the water was 
boiling. On placing the empty bulb in a freezing mix- 
ture, the vapor of water is so rapidly condensed as to freeze 
the fluid in the ball which is remote from the freezing 
mixture, and which is usually protected by an envelope of 

144. Dew- Point — If we drop bits of ice into a tumbler 
of water (one of polished silver is best) having the same 
temperature with the air, and watch the fall of a thermo- 
meter placed in it, we can denote with accuracy the temper- 
ature of the water, when it has cooled so far that moisture 
begins to be deposited on the clean surface of the glass. 
This temperature is called the dew-point ; and the number 
of degrees between it and the temperature of the air is an 
accurate indication of the actual dryness of the air. In 
this climate, in summer, this difference amounts often to 
40° or more, and in India it has been known to be as much 
as 61° ; that is, with an external temperature of 90°, the 
dew-point has been seen as low as 29°. The amount of 
moisture in the air has an influence on the indications of 
the barometer, and it is always requisite, in making baro- 
metrical observations, to make a correction for the tension 
of the vapor of water in the air. 

Several common facts are explained by a reference to these 
principles. When the air is highly charged with humidity, 
it deposits dew on any substance colder than itself. A glass 
of iced water in summer is immediately covered with a coat of 
condensed vapor ; when a warm humid morning succeeds a 
cool night, we see the pavements and walls of the houses 
reeking with deposited water, as if they had been drenched 
with rain. The fall of dew (as has been already explained) 

Describe the cry ophorus. 144. What is the dew-point? Howobserred? 
What common facts are explained by it ? 





occurs in consequence of the radiation from the earth re* 
ducing its temperature below the " dew-point." 

145. Hygrometers are instruments to determine the 
amount of moisture in the air. One much used is called 
the wet bulb hygrometer, (fig. 118,) or psych ro- 
meter, and consists of two similar delicate mer- 
curial thermometers, the bulb of one of which is 
covered with muslin and is kept constantly wet 
by water, led on to it by a string from a tube in 
the centre. The evaporation of the water from 
the wet bulb reduces the temperature of that 
thermometer to which it is attached, in propor- 
tion to the dryness of the air, and consequent 
rapidity of evaporation. The other thermometer 
indicates the actual temperature ; and the differ- 
ence being noted, a mathematical formula ena- 
bles us to determine the dew-point. 

146. But a much more delicate instrument for 
this use is that of Mr. Daniell, which is con- 
structed on the principle of the cryophorus, (143.) 
It is represented in fig. 119. The long limb 
ends in a bulb, which is made of black glass,* that 
Fig. 118. the condensed vapor may be more easily seen 
•n it. It contains a portion of ether, into which dips the 
flail of a small and delicate thermometer contained in the 
cavity of the tube. The whole instrument contains only 
the vapor of ether, air having been removed. The short 
limb carries an empty bulb, which is 
covered with muslin. On the support is 
I another thermometer, by which we can 
observe the temperature of the air. When 
an observation is to be made by this in- 
strument, a little ether is poured on the 
muslin : this evaporates rapidly, and of 
course reduces the temperature of the 
other ball. As soon as this has fallen 
to the dew-point, the moisture collects 
and is easily seen on the black glass. 
At this instant, the temperature indicated 
Fig. 119. by the two thermometers is noted, and 

145. What are hygrometers ? Describe the wt?t bulb. 146. Describe 
Darnell's. What is the principle of Daniell's? Which is the best' 





to* difference gives us the true dew-point. The latest and 
most improved form of hygrometer is that of Regnault: it 
involves the principle of DanielPs, with important means of 
additional accuracy. 

147. Diffusion and Effusion of Gases and Vapors. — The 
vapor of water will rise and fill a confined vessel of air, and 
have the same tension as if no air were present. It will 
take a longer time to do it, but as much will ultimately rise 
as if the space were a vacuum. The air seems to be an 
impediment only to the rapid rise of the vapor. On the 
same principle, probably, is explained the curious & 
and important fact, that, when different gases are 
in contact, they will not remain separate, but will 
soon mingle uniformly, even against the force of 
gravity. Our atmosphere, for instance, is composed 
of two gases, the specific gravities of which are as 
976 to 1130, and we might suppose that the heavier 
would be at the bottom, as would be the case in two 
such liquids as water and oil. But they are found 
to be in a state of uniform mixture. If we connect 
together by a narrow tube two bottles, (fig. 120,) 
containing, one a light gas, hydrogen, and the other 
a heavier gas, oxygen, and place the heavy one 
uppermost, in a few hours we shall find them per- 
fectly commingled ; as may be proved by the fact 
that the mixture will explode violently on touching Fi «- 12 °* 
a match to the open mouth of one of the vessels, 
which we know a mixture of these two gases 
will always do. 

148. If we fill the end of a glass tube 
(fig. 121) of moderate size with a plug of 
plaster of Paris, we form what is called 
Graham's diffusion tube. When the plaster 
is dry j if the tube be filled, for example, 
with hydrogen gas, and its open end intro- 
duced into a vessel of water, this liquid is 
seen to rise rapidly, owing to the escape of 
the light gas into the air. At the same time 
the air enters the tube, and renders the mix- 
ture explosive ; but nearly four volumes of Fig. 121. 

147. What is meant by diffusion of gases ? Give an ilfcrctration. 14S. 
iVhat is the diffusion tube ? In what proportion does the air enter? 



98 HEAT. 

hydrogen escape for one of air which enters, and these are 
called the diffusion volumes of hydrogen and air. Every 
gas has its own diffusion volume depending on its density, 
these being inversely as the square root of the densities of 
the gases. The same law pertains to the rapidity with which 
gases rush into a vacuum through a minute orifice. 

149. The passage of gases through moist membranes is 
connected with this subject, but involves also another con- 
dition, viz. the solubility of certain gases in water. For 
example, a bladder partly full of air, and tied tightly at the 
neck, is introduced into an air-jar full of carbonic acid; 
after some hours the bladder is found much distended, and 
may finally burst, from the passage of the carbonic acid gas 
into it. This is effected by the solubility of this gas in 
water : it thus passes the pores of the membrane, and is 
rapidly diffused again in the air of the bladder. Dr. Mitchell 
found that the time required to pass the same volume of 
several gases through the same membrane was 1 minute 
for ammonia, 2 J minutes for sulphuretted hydrogen, 3} for 
cyanogen, 5 J for carbonic acid, 6} for nitrous acid, 28 for 
olefiant gas, 37 J for hydrogen, 113 for oxygen, and 160 for 
carbonic oxyd. For nitrogen the time was much greater. 

150. Liquefaction and Solidification of Gases. — In 1823, 
Faraday first demonstrated the possibility, by united cold 
and pressure, of reducing several gases to the liquid and 
even solid state. The apparatus originally employed in 
these interesting but hazardous experiments, was simply a 

stout glass tube, bent as 
in figure 122, containing 
the materials to evolvo 
the gas, and heated at 
» both ends. If cyanogen 
Fig. 122. is to be liquefied, dry 

cyanid of mercury is placed in one end of the tube, and 
heated, while the empty end is cooled in a freezing mixture : 
the cas, accumulating in a narrow space, is liquefied by 
the force of its own elasticity. Some hazard attends these 
experiments, and the operator should be protected by gloves 
and a mask of wire-gauze. In this way, chlorine, cyanogen, 

What is the law of diffusion? 149. What of the passage of gasoi 
through membranes ? Give an example. What are Mitchell's results t 
150 Who first liquefied gases ? What was tho means? 





carbonic acid, nitrous oxyd, and several other gases have 
seen reduced to the liquid state, and some to the solid con* 
dition. Several of these gases — as ammonia, cyanogen, and 
sulphurous acid — may be liquefied by cold alone, without 
additional pressure. 

151. M. Thilorier's apparatus for liquefaction of carbonic 
acid involves the same principle. In fig. 123, g is the gene- 
rator of the gas, a strong cast- 
iron vessel, hung by centres on 
a frame /; in it is put the 
requisite quantity of carbonate 
of soda and water, and a tube a 
of copper, holding an equivalent 
amount of strong sulphuric acid ; 
the cap of red metal is strongly 
screwed in, the valve closed, 
and the position of the appa- 
ratus inverted, by turning it 
over on its centres; the acid 
then runs out among the car- 
bonate of soda, and an enor- J 
mous pressure is generated by Fi 123 

the successive portions of gas 

evolved. After a time, when the action is complete, the 
generator is connected by a metallic tube with the receiver 
r; stopcocks, simple screw-plugs having a conical point, 
confine the gas, and being opened, the liquefied gas collects 
in r, which is cooled by a freezing mixture for the purpose 
of condensing it. In this way, several successive quarts of 
.the liquid carbonic acid gas are accumulated in r. A por- 
tion of this liquid may be safely drawn off into a strong 
glass tube refrigerated. It can then be drawn off by a jet 
j secured to the top, which enters a metallic box b with 
perforated wooden handles. The rapid evaporation of a 
part of the liquid gas absorbs so much heat from the rest, 
that a considerable portion is converted to a fine white solid, 
like dry snow, which fills the box. When once solidified, 
it wastes away very slowly, and may be handled and 
moulded with ease. If suffered to rest on the hand, how- 
ever, it destroys the vitality of the flesh, like a hot iron. 
It is now in a condition analogous to bodies in the spheroidal 

What gases have been liquefied ? Describe Thilorier's apparatus. 




state (181 ;) being surrounded by an atmosphere of its owa 
vapor, the radiation of heat to it from surrounding bodies is 
cut off, and it acquires the very low temperature of — 140°. 
If it is wet with ether in a capsule containing mercury, th* 
latter is frozen solid, and can ; then be hammered with a 
wooden mallet, and drawn out like lead. When moistened 
with ether in vacuo, with certain precautions, the very low 
temperature of — 166° is produced. Carbonic acid at 0° has 
a tension of nearly 23 atmospheres ; at 32° its tension is 
38 J atmospheres; at —84°, 12}; at —75°, 4.60; and at 
— 111°, 1-14 atmospheres. It becomes at — 71° a clear 
transparent solid, sinking in the surrounding fluid. 

This apparatus once exploded in Paris, killing the assist- 
ant in a frightful manner. l It is, however, due to Mr. 
Chamberlain, of Boston, to say that the author has re- 
peatedly used several of these instruments of his construc- 
tion with entire safety. 

152. By the use of mechanical pressure, and the enor- 
mously low temperature of the bath of carbonic acid and 
ether in vacuo, Faraday has succeeded in reducing several 
other gases to the liquid or solid state. These facts will be 
mentioned under the history of the several substances. 

The greatest artificial cold hitherto observed is 220° below 
zero of Fahrenheit, and was obtained by Natterer, with the 
aid of a bath of liquid nitrous oxyd and sulphuret of carbon 
in vacuo. The greatest natural cold recorded is — 76° below 

Several gases have resisted all attempts to reduce them to 
a liquid state, viz. hydrogen at 27 atmospheres; oxygen at 
58} ; nitrogen, nitric oxyd, and carbonic oxyd at 50, and coal 
gas at 32 atmospheres, aided by the greatest artificial cold. 


153. More than 600 years b. c. the ancients observed in 
amber a remarkable power of excitation by friction. Mo- 
dern science has conferred on this power the name of elec- 
tricity, from the Greek word for amber, (electron.) This 
force, or power, has various modes of existence or manifesta- 

152. How has Faraday reduced other gases? What is the lowest 
temperature observed? What in nature? What gases hay© resisted 
liquefaction? 153. What was the first electrical observation? 




tion, which are chiefly, 1. Magnetic electricity; 2. Fric- 
tional, or statical electricity; 3. Dynamical, voltaic, or gal- 
vanic electricity, (from chemical action ;) 4. Thermo-elec- 
tricity; and, 5. Animal electricity. 

Magnetic Electricity, or Magnetism, 

154. Lode-stone, — A kind of iron-ore has heen knowi 
from remote antiquity, that has the property of attractiir, 
to itself small particles of iron; this is called 
the lode-stone. By contact, it can impart its 
virtues to iron and steel, and also, to a consider- 
able degree, to cobalt and nickel. As it 
abounded in Magnesia, it wfe called by Pliny 
rnagnes, and hence the name magnet This ore 
mounted in a frame of soft iron 11, (fig. 124,) f{ ^ 124 
constituted the original magnet : pyf are the 
poles. A bar, or needle of steel, which has received the 
magnetic influence, when suspended on a point, 
will be found to have a directive tendency, 
by which one end turns invariably to the 
north. The needle, therefore, has polarity, 
and the end turning north is called the north 
pole, and the other end the south pole. 

155. Polarity. — If we bring the north end 
of a magnetic bar near to the similar end of g * 125# 
the suspended needle, the latter will move away, as indi- 
cated by the arrows, being repelled by the similar power of 
the bar. If, however, we bring the end N - -.^...^a 
toward the opposite end of the needle S, it IP ^' — IW 
will be attracted to the bar, and strive to move Flg * 126# 
as near to it as possible. The reverse is, of course, true of 
the opposite end of the bar. If, in place of a magnetic bar, 
we had used a bar of unmagnetic iron, we should have found 
both ends of the suspended needle equally, but less power- 
fully, attracted by it. We thus learn (1) that the magnet 
has polarity ; and (2) that poles of the same name repel, 
and those of opposite names attract each other. 

156. Induction of Magnetism. — The manner in which a 
magnet, or lode-stone, imparts its own power to surrounding 

What modes of electricity are named? 154. What is the lode-stone ? 
What is the needle? 155. What is polarity? What is the law of r*. 
pulsion? 156. What is induction ? 





i«l substances, is called induction , and those 

bodies capable of manifesting this power 
are said to be magnetized by the tn- 
ductive influence. Thus, a series of 
bars of soft iron laid about a magnetic 
bar, as in the figure, will all become 
temporarily magnetic by induction ; and 
in obedience to the law just stated, 
their ends next the N are all S, and 
their remote ends all N. Every mag- 
Fig. 127. ne ^ g0 to gpea]^ j s surrounded by an 
atmosphere of influence, which has its centre in the poles 
of the magnet, and diminishes in intensity inversely as the 
square of the distance. This decrease of force is 
prettily illustrated by an experiment shown in the 
annexed cut. The bar magnet holds a large key ; 
this can hold a second smaller than itself; this, a 
nail ; the nail, a tack-nail \ and lastly, a few iron- 
filings are held by the tack-nail; and the whole re- 
ceive their magnetism by induction from the bar, 
and each article has its own separate polarity. In- 
duction takes place through a glass-plate, or any 
similar substance. 

157. Permanent magnets can be made only of 
hardened steel. Soft iron and steel become mag- 
nets only while under the influence of other magnets, 
and lose their own power as soon as removed from 
them. Magnetism is imparted by ' touch, 9 as it is 
technically called, from a previously existing mag- 
net. An unmagnetic bar of hardened steel, when 
properly rubbed by the poles of a magnet, will itself 
soon acquire polarity and magnetic power. Mag- 
Fig. 128. netism is thought to rest mostly on the surface of 
the metal. Every magnet is regarded as made up of a 
great number of small magnets, so to speak, each particle 
of steel having its own polarity. We cannot conceive of one 
n«n«n«n«n«n«n« »« sort of polarity existing 
N » E5 S5 F™ T 9 * ^^ r ™ '- JB * S w ^^ out tne ofc her. Thus, 
c5c3l§E!^!i5il5ciisEH in figure 129, we see a 
Fi 129# magnified representation 

Explain figs. 127 and 128. 157. What aro permanent magnets ? What 
U attraction and ' touch' ? How are the forces in a magnet distributed ? 




of this condition. Each little magnet has its own n and s. 

Those which occupy the middle of the bar, being acted on 
alike in all directions, can show no power ; but the force 
accumulates toward each end, until we find the greatest 
power in the last range of particles, which we term the 

If we dip a magnetic bar in iron-filings, we shall find only 
the ends attracting a tuft of the metallic particles, while the 
middle is free. If two magnetic bars, however, like the 
figure, are placed together, (-{- and — ,) and a sheet of 
paper laid over them, they will attract iron-filings scattered 
on the paper, in the way .ysff^\ i T i u^--''^ i ^^W l 1/^y- 

here a pair of central poles ^1:^E!»mb!Z3^^^__^^B^^ 

part of the simple bar had Fig. 130. 

not. The particles of iron arrange themselves in what are 
called magnetic curves. These curves represent very nearly 
the lines of magnetic force which always environ a magnet, 
and tend to impart magnetic properties to all bodies — solid, 
liquid, or gaseous — which come within their range. 

158. Artificial Magnets are made of all forms, the most 
common being the so-called horse-shoe magnet, shaped like 
figure 131. It is found that the power of magnets ■ ■ 
is much increased by uniting several thin plates of W 
hardened steel, each of which is separately magnet- Fi S« 131 » 
ized. A bar of soft iron, called the keeper, is placed across 
the poles of the horse-shoe magnet, to prevent it from losing 
power; and if it be made to hold a weight nearly equal to 
the power of the magnet, it will be found to gain strength daily 
up to a certain point, and in like manner to lose its magnet- 
ism if unemployed. Artificial magnets, weighing one pound, 
have been made to sustain 28 times their own weight. 

159. The Earth'* Magnetism. — The earth is regarded as 
a great magnet. Its power is equal, according to Gauss, to 
that which would be conferred if every cubic yard of it con- 
tained six one-pound magnets. The sum of the force is 
equal to 8,464,000,000,000,000,000,000 such magnets. 
The magnetism which we see in bars of steel and the lode- 

Dlustrate this as in fig. 129. 158. How are magnets formed and pre- 
served ? What is terrestrial magnetism ? What its foroe in a cubic yard f 




ftone is the result of induction from tbe earth. Magnetism 
from the earth is induced in all bars of steel or iron which 
stand long in a vertical position. Tongs and blacksmiths' 
tools are often found to be magnetized. A bar of iron held 
in the magnetic meridian, and at the proper inclination, 
becomes immediately magnetic from the induction of the 
earth ; and the effect may be hastened by striking it on the 
end with a hammer : the vibration seems to aid in inducing 
the magnetic force. The tools used in boring and cutting 
iron are also generally found to be magnets. The magnetic 
poles of the earth are not in the same points with the poles 
of revolution or the axis of the earth, and for this reason 
the magnetic needle does not point to the true north and 
south, but varies from it more or less, and differs at different 
times, as the magnetic pole alters its position. This is 
called the variation of the needle. 

160. Dipping Needle. — The magnetism of the earth is 
beautifully shown by the dipping needle, represented in the 

annexed figure. The needle n is sus- 
pended on the horizontal bar a, so as 
to move in a vertical plane, instead of 
horizontally, as in the compass-needle. 
The graduated vertical circle c is placed 
in the magnetic meridian, and the needle 
then assumes, in this latitude, (41° 18',) 
D the position shown in the figure, dipping 
Fig. 132. at an angle of 73° 27'. Over the mag- 

netic equator it would stand horizontal, being equally at- 
tracted in both directions. At either magnetic pole it would 
be vertical. The horizontal variation of the needle, its dip, 
and the intensity of the polar attraction, are subject to daily 
and local changes, from the fluctuations of temperature in- 
fluencing the magnetic conditions of the atmosphere, as 
shown by the late results of Faraday. 

161. Magnetics and Diamagnetics. — Dr. Faraday, in 1845, 
made the important discovery that all solid and liquid sub- 
stances, and many gases, were subject to the magnetic in- 
fluence. According to his results, confirmed by numerous 
subsequent observers, all bodies may be subdivided into two 
great classes — the magnetic and diamagnetic. To the first 

How are objects affected by it? Where are the magnetic poles ? 160. 
What is the dipping needle ? What is said of variations in dip, <kc ? 




class belong all bodies which act like iron and nickel — that 
18, which place themselves, when suspended as a needle, 
axiaUy or in the line connecting the poles of a magnet — 
and which also exhibit the familiar mode of attraction by 
either pole of a magnet alike. The bodies belonging to this 
class are either metals or oxyds and salts of metals, (both 
solid and liquid.) To the second class belong all liquids 
and solids which do not belong to the magnetic class. Bis- 
muth appears to be the most remarkable substance in 
diamagnetic energy. A suspended needle of this metal 
places itself at right angles to that position which iron 
assumes under the same circumstances. A few bodies of 
each class are enumerated in the following list, where we 
observe that iron and bismuth are at the extremes, each 
standing as the type of its own class, while air and vacuum 
occupy the zero, or neutral point of quiescent inactivity : — 
Iron, nickel, cobalt, manganese, palladium, crown-glass, 
platinum, osmium, — 0°, air and vacuum, arsenic, ether, 
alcohol, gold, water, mercury, flint-glass, tin, heavy glass, 
antimony, phosphorus, bismuth. It is a curious sight to see 
a piece of wood, or of beef, or an apple, or a bottle of water, 
repelled by a magnet; or, taking the leaf of a tree and 
hanging it up between the poles, to observe it take an 
equatorial position. 

162. The latest results of Faraday show that oxygen gas 
is to be reckoned as a magnetic, having about 3 J 5 th part the 
capacity of iron for magnetic induction. This fact connects 
itself in the most important manner with the magnetic con- 
dition of the atmosphere — the daily variations in dip and 
intensity — as probably also with the aurora borealis. 

Electricity of Friction, or Statical Electricity. 

163. Statical electricity is evolved by several of the same 
causes which we have named as sources of heat. Friction 
excites it abundantly ; chemical action still more so. It 
attends animal life, and is powerfully exhibited in some 
animals, as in the torpedo and electrical eel : heat evolves 
it, as in the mineral tourmalin; and we have reason to 

161. What axe magnetics and diamagnetics? Name some of them. 162. 
What is Faraday's discovery regarding oxygen ? 163. What are sources 
of (fictional electricity ? 




believe that the sun's rays are perpetually exciting electric*, 
currents in the earth. Like heat, it neither adds to nor sub* 
tracts from the weight of matter ; but, unlike heat, it pro- 
duces no change in dimensions, and does not affect the power 
of cohesion in bodies. In powerful discharges, however, it- 
overcomes cohesion by rending or fusion. All matter is 
subject to its influence, and it can be transferred from an 
excited body to one previously in a neutral state. 

We shall treat this curious and most interesting subject 
very briefly, as its chemical relations are much more limited 
than those of galvanism. 

^^ 164. Electrical Excitement — If we briskly 

-JV,\.. rub a glass tube with warm and dry silk, and 

" bring it near to any light substance, as some 

Pie 133 P* fcD > 0D ^ e te ^ e > (fifr 1^>) a fl 00 ^ °^ cot " 

ton, some shreds or silk, or, as in fig. 134, 

to two balls of pith suspended on a hook by delicate wire, 

the light substances will at first be strongly attracted to the 

tube, but in an instant will fly from it, as if 

I repelled by some unseen force ; and any further 

ft effort to attract them to the excited glass will 

/ \\ only cause their continued removal. Each se- 

/ \ \, parate thread of silk and each pith -ball seems 

O <X & to retreat as far as possible from the glass tube 

Fie. 134. an( * fr° m * te f e N° ws * W> * n * ne P* ace °* tne 

glass tube, we use a stick of sealing-wax rubbed 
with dry flannel, and present this to the light substances 
which have been excited by the glass tube, we shall find a 
very strong attraction manifested between them : the light 
substance previously excited by the glass will move to the 
excited resin much more actively than a substance not pre- 
viously excited in this way ; and two substances separately 
excited, one by the glass and the other by the resin, will 
attract each other with equal power. The first of these is 
called vitreous, and the second resinous electricity. These 
simple phenomena form the basis of all electrical science. 

165. Electrical Polarity. — There is a strong analogy be- 
tween the two sorts of electrical excitement and the opposite 
powers of the magnet. The vitreous is to the resinous elec- 

What similarity has it to heat? What differences ? 164. How do you 
excite a glass tube ? How does it affect pith-balls, Ac. ? How if wax \* 
l*d ? 165. What is electrical polarity ? 





Q -Q + 0+^i-.^4- 

tricity as the north 

pole of a magnet is 

to the south. Hence 

we call the vitreous 

the positive electri- Fig. 135. 

city, and the resinous the negative electricity. A row of pith • 

balls, (fig. 135,) when excited by induction, or influence, stand 

related to each other as shown by the signs plus and minus. 

166. Electrical machines are constructed for the easy ex- 
citation of large quantities of electricity. Two forms of 
this machine — the cylinder 
and the plate — are in com- 
mon use. In the plate ma- 
chine, (fig. 136,) ci is a 
wheel or plate-glass, turned 
on an axis by a handle m. 
The electricity is excited by 
the friction of two cushions 
or rubbers pressing against 
the plate, and covered with 
a soft amalgam of mercury, 
tin, and zinc, which greatly 
heightens the effect. The 
rubbers are connected with the earth by a metallic chain. 
The excited glass delivers its electricity to several sharp 
points of wire attached to the bright brass arms it, and 
connected with the great conductors fg. The conductors 
are perfectly insulated by glass supports h h. 

In the cylinder machine, (fig. 137,) a hollow cylinder of 
glass v is used, to excite the electricity ; c is the rubber, 
and a r are the prime 
conductors. When* 
the winch is turned, JL^ 
bright sparks of a* 
violet color, form- 
ing zigzag lines like 
lightning, dart with 
a sharp sound to any 
conducting substance 
brought near to the 

Fig. 13d. 

Fig. 137, 

How is it like magnetic ? 166. What is the plate machine ? What th» 
cylinder ? Describe figs. 136 and 137. 





great conductors. This is positive electricity. If negative 
electricity be wanted, we must insulate the rubbers, and, 
sonnecting the opposite conductor with the earth, draw the 
sparks from the rubber. For this purpose, the construction 
in fig. 137 is most convenient. Every care must be taken, 
in the use of an electrical apparatus, to keep it 
clean and smooth, and particularly free from moist- 
ure. Warm flannel or silk is to be used to wipe the 

167. Electroscopes, or Electrometers. — The quad- 
rant electroscope (fig. 138) is usually attached to the 
prime conductor, to indicate the activity of the ma- 
chine by the more or less elevated angle assumed 
by the arm. The pith-balls of fig. 135 answer the 
Fig. 138. same purpose, and may also denote the kind of excite- 
ment. For example, if they are excited by glass, 
on approaching them with another excited body, 
if they are attracted, then we know that the 
second body has negative excitement — if re- 
pelled, positive excitement is found. 

The gold-leaf electrometer (fig. 139,) is, 
however, a much more delicate test of electri- 
cal excitement. It consists of two leaves of 
gold, suspended in an air-jar, and communi- 
j eating by a wire with a small plate of brass ; 
' the approach to this plate of a body in any 
degree excited, will occasion an immediate 
movement of the gold-leaves, from which we 
can tell the nature of the excitement, as 
above described, having previously imparted 
to the gold-leaves a particular kind of elec- 

168. ColomVs torsion electrometer, (fig. 
140,) allows of the exact measurement of 
quantities of electricity. A slender rod of 
gum-lac (j, with ends of gilt pith, is suspend- 
ed within a glass shade a by a filament of 
I glass depending from the tube/. Another 
bar of lac, also with gilt pith-balls, (called 
Fig. 140. the carrier-bar,) is introduced at pleasure 

Fig. 139. 

What is an electroscope ? Describe the gold-leaf. 168. Describe Co. 
tomb's electrometer, fig. 140. What does it enable us to do ? 




by an opening o in the cover of the instrument. By a screw 
t at top the needle may be adjusted. When unexcited, the 
needle and carrier-bar stand in close proximity. To mea- 
sure electricity by this instrument, the lower ball of the 
carrier-rod is charged and introduced into the cylinder. It 
will repel the movable ball in proportion to the intensity of 
the charge ; and by turning the milled head at m we may 
measure the degree of deflection, or torsion, of the thread 
of glass. This we can also note on the graduated circle upon 
the cylinder. 

169. Conductor* and Insulators of Electricity. — The 
pith-balls or glass tubes, which have been electrically ex- 
cited, return to a natural state very slowly indeed, if left 
untouched, in dry air. But the hand, or a metallic rod, 
will at once restore them to the unexcited state, while dry 
silk, glass, and resin will not remove the excitement. 
Bodies are, therefore, divided into conductors and non-con- 
ductors of electricity, or, more properly, into good and bad 
conductors. The electrical discharge takes place through 
good conductors (as the metals) with an inconceivable 
velocity, which can be compared only to the velocity of 
light. Among good conductors, in the order of their con- 
ducting power, are the metals, charcoal, plumbago, and 
various fused metallic chlorids, st^ng acids, water, damp air, 
vegetable and animal bodies ; among bad or imperfect con- 
ductors are spermaceti, glass, sulphur, fixed oils, oil of tur- 
pentine, resin, ice, diamond, and dry gases. The latter 
substances are also called insulators, because by their aid we 
tan insulate or confine electricity. 

170. The distribution of electricity in an excited body is 
apon the surface. In proof of this, if on the insulated 
stand b (fig. 141) we excite a spherical 
body c c, provided with glass handles, 
we may separate its halves and observe _. 
that the inner sphere a has no excite- If 
ment whatever. All the electricity ^mk> 
remains on the outer surface. If the tfig. hi. 

body is egg-shaped, the excitement becomes more concen- 
trated in the extremities. A small point at the end of the 
prime conductor will convey off all the excitement of a power- 

169. What are conductors and insulators ? Name some of each, 170. How 
Is electricity distributed ? Describe fig. 141; What is true of a point on 
the prime conductor ? 

, 11 VU. bUO lUBUUkbCU 




ful machine insensibly, unless in the dark, when a track of 
light will be seen proceeding from the point. 

The excitement of a powerful machine may be 
withdrawn by pith-balls, or figures of pith ar- 
ranged as is figure 142, which convey away the 
electricity as fast as it is produced — being at- 
tracted and repelled between the two surfaces. 

171. Lightning conductors were devised by 
Dr. Franklin, after his memorable experiment 
with the kite, by which he proved the identity of _ 
atmospheric electricity with that of machine ex- e 
citation. The efficacy of lightning conductors, Fi «- 142 - 
now so general, depends on the power of a point to draw 
away insensibly very powerful charges of electricity. It is 
essential that they should be well insulated, and that the 
lower end should enter so deep into the earth as always to 
be in damp ground. 

172. Two theories have been proposed to explain the 
ordinary phenomena of electricity. The first is called the 
Franklinian hypoiliesis, proposed by our distinguished 
countryman, Dr. Franklin. It supposes that there is a 
simple, subtle, and highly-elastic fluid, which pervades all 
matter. This fluid is self-repellent, but attracts all matter, 
or its ultimate particles. In the natural state of bodies, 
this fluid is uniformly distributed over them, and its in- 
crease or diminution produces electrical excitement. Ac- 
cordingly, when a glass tube is rubbed with a silk hand- 
kerchief, the electrical equilibrium is disturbed, the glass 
acquires more than its natural quantity, and is over-charged, 
the silk possesses less, and is under-charged. 

The second hypothesis is that of Du Fay, who assumes that 
electrical phenomena are due to two highly elastic, impon- 
derable fluids, the particles of which are self-repellent, but 
attractive of each other. These two fluids exist in all un- 
excited bodies in a state of combination and neutralization, 
when no electrical phenomena are seen. Friction occasions 
the separation of the fluids, and the electrical excitement in 
a body continues until an equal amount of opposite electri- 
city to that excited has been restored to it. 

How do the dancing figures discharge electricity? 171. How do 
lightning conductors act? 172. What is the Franklinian hypothesis? 
What is that of Du Fay ? 





According to Dr. Franklin's theory, the two states am 
denominated positive and negative ; according to Da Fay, 
they are distinguished as vitreous and resinous. 

Whichever theory we may adopt, we can clearly see how 
it is impossible ever to develop one electrical condition 
without at the same time giving rise to the other. 

173. The Ley den jar was invented by Cunasus, of 
Leyden, in 1746. By it the experimenter collects and 
transfers a portion of the electricity evolved by his machine, 
and applies it to the purposes of experiment. It is simply 
a glass jar, (fig. 143,) covered inside and out with tin-foil up 
to the line seen in the figure. A brass ball 
communicates by a wire and chain with the in- 
terior coating, the mouth being stopped by a 
cover of dry wood. On approaching the ball 
to the conductor of the electrical machine, 
when in action, a series of vivid sparks will be 
received by it, and a great accumulation of 
vitreous electricity takes place in the interior, 
provided the exterior be not insulated. On 
forming a connection by a conductor between 
the interior and exterior surfaces, the equili- 
brium is at once restored by a rush of the op- 
posing forces, accompanied with a brilliant flash of artificial 
lightning. If the hand of the operator is the conducting 
medium, a violent shock is felt, commonly known as the 
electrical shock. A series of such jars, arranged so as to be 
charged by one machine, is called an electrical battery, as 

shown in figure 144, where all 
the inside coatings unite, and 
also all the outsides are con- 
nected. The battery may also 
be so constructed as to allow of 
the jars, after they are charged, 
being shifted so that the series 
shall be discharged consecutive- 
s— ly, each outer connected with 
the next inner coating. Great 
intensity is thus obtained. 

Fig. 144. 

What terms describe these conditions? 173. What is the Leyden 
)ir ? What its theory ? What is an electrical battery 1 


174. By using an insulated 

? Y jointed rod, fug. 145,) called a 

\ I discharging roa, the experimenter 

\ / avoids receiving the shock. 

\* «/ When the shock of the electri- 

^^■^^ cal battery is passed through 

a card, (fig. 146,) the hole which is 

Fig. 145. pierced is burred on both sides. 

This fact has been adduced as a proof that there 

were two fluids, moving in different directions. 

Otherwise it would seem that the burr should 

exist only on one side. 

175. The dissected Leyden jar (fig. 147) is Fig. 146. 
so constructed that we may remove the interior 
coating from its glass jar b, leaving the outer coat- 
ing alone. This may be done after the jar is 
charged, when the separate parts will not manifest 
excitement, as tested by the electroscope. When 
reunited, however, a spark can still be drawn 
from it. 

If the Leyden jar is placed on an insu- 
lating stand «, (fig. 148,) it will be found 
impossible to charge it. The most power- 
ful machine a will communicate only one or 
[C^ two sparks to it, 6. This is because the 
■ ' I negative excitement cannot pass off from 
the outer coating. Accordingly, if the ball 
i JL of a second jar c, uninsulated, be brought 
Fig. 148. near t De outer coating, a torrent of sparks 
flows off, and both jars are quickly charged. Attention to 
the laws of attraction and repulsion gives us an easy solu- 
tion of this problem, which involves the whole theory of the 
Leyden jar. It is also obvious that glass is not an impedi- 
ment to the induction of electrical excitement, however per- 
fect it may be as a non-conductor. 

176. Dr. Faraday has shown that the inductive action of 
ordinary electricity takes place in curves which are analo- 
gous to the lines of force surrounding a magnet — forming its 
atmosphere of influence, so to speak. 

174. What is a discharging rod? What does the card experiment 
show ? 175. What is the dissected jar ? Describe the experiment in 
fig. 148. 176. How does electrical induction occur? Name the induc- 
tive power of glass, lac, sulphur, Ac. 




Substances also differ in their specific power of inductive 
capacity : thus, air being unity, the inductive capacity of glass 
is 1-76, of lac 2, and of sulphur 2-25. All gases also have 
the same inductive capacity, however they may differ in 
density or other respects. 

177. The Electrophorus is a convenient mode of obtain- 
ing an electrical spark, when no 
electrical machine is to be had, 
and consists of a shallow tray 
of tin, the size of a dining plate, 
partly filled with melted shellac , 
a, or some other resinous pre- 
paration, made as smooth as 
possible. A disc of brass 6, Fig. 149. 

with a glass handle, is provided, and the bed of resin is 
rubbed with a dry flannel or cat-skin : this excites negative 
electricity, and the metal disc is then laid on the excited 
surface, and touched with the finger, which receives a nega- 
tive spark. A coating of positive electricity is induced on b, 
which may be raised, and discharged by a conductor, giving 
a vivid spark, sufficient to explode gases. The resinous 
electricity not being conducted away from the shellac, the 
spark may be repeated as long as the excitement lasts. It 
is plain that the electricity in this case is induced by the 
excited lac. 

If a mixture of red-lead and flowers of sulphur, previously 
well mixed in a mortar, be blown from a tube over the ex- 
cited surface of the electrophorus, the two substances are 
immediately separated, because of their opposite electrical 
relations, and are arranged in curious figures on opposite 
sides of the excited disc. 

178. A jet of high steam, issuing from a locomotive or 
other insulated steam-boiler, will, with certain precautions, 
give a stream of electrical sparks more powerful than any 
electrical machine. This has been called hydro-electricity, 
and is produced by the friction of the hot steam on the 
edges of the orifice from which the steam issues. 

177. What is the electrophorus? What is its theory? How dow 
led-lead, Ac. behave on it ? 178. What is hydro-electricity ? 





Galvanism, Voltaism, or Electricity of Chemical Actum. 

179. History. — Galvani, of Bologna, in the year 1790, 
accidentally observed that the freshly denuded legs of a frog, 
suspended on a metallic conductor, were powerfully con- 
vulsed when brought near to an active electrical machine. 
From this trivial observation has sprung one of the most 
wonderful departments of human knowledge. The same 
fact had been previously noticed, and Swammerdam had 
exhibited it before the Grand Duke of Tuscany, but no 
result of value was deduced from it. It was suggested that 
there was a peculiar sensitiveness to electrical excitement 
in animal substances, due to some remaining vital energy. 
This explanation failed to satisfy Galvani, who observed 

similar convulsions in the frog's limbs when 
. hanging from a copper wire b (fig. 150) on 
_* an iron rail. He found that the effects were 
produced whenever the muscles touched the 
iron while the nerves touched the copper, but 
that contact with the copper alone did not 
produce them. The crural nerves are easily 
exposed by separating the large muscles with 
the fingers at a a. From his observations, 
Galvani inferred that there was a peculiar 
variety of electricity in animals, which he 
called animal electricity — that this was de- 
veloped whenever connection was made be- 
tween the muscle and naked nerve by means 
of two metals. This theory fascinated the 
physiologists, and for ten years Galvani's experiments wero 
repeated with great zeal in all civilized countries. 

180. Volta, of Pavia, maintained that it was the contact 
of two metals which generated the electricity, of which the 
frog's legs were only a delicate electroscope. This experi- 
ment can never fail to excite wonder, however often we may 
perform it. We suspend from a metallic conductor a pair 
of frog's legs recently skinned, and with a part of the spino 
attached. With two metallic slips, one of zinc and one of 
copper, we touch at the same time the naked nerve and the 

179. What was Galvani's observation? What was the suggestion? 
What did Galvani infer? How was his animal electricity excited 
180. What did Volta maintain? What was his observation with the 
frog's legs ? 

Fig. 150. 





Fig. 151. 

muscle, as shown in fig. 151. Convulsions 
immediately throw the limbs into the po- 
sition indicated by the dotted lines ; and 
we may repeat the trial until, after a time, 
this power gradually dies out. In proof 
of his views, Volta invented and brought 
forward his memorable pile, of which a 
more particular mention will be made 

181. This is not the place to record in detail the history 
of science, but this discovery is one of the few grand 
achievements of the human mind which must ever mars 
the moment of a new era in experimental philosophy. It is 
both wonderful and instructive to reflect that so simple an 
observation as the twitching of a frog's legs should have led 
immediately to a revelation of the metallic basis of the en- 
tire crust of our planet — to the adoption of a new classifica- 
tion of elements and of their compounds — to almost mi- 
raculous performances in metallurgy — and to the instanta- 
neous communication of thought, by the annihilation of 
time and space ! 

182. Voltaic Pile. — Volta sagaciously reasoned that the 
effects observed by Galvani could be produced with simple 
metals and a fluid, or substances saturated with a fluid. The 
truth of this conjecture is easily verified by placing on the 
tongue a silver coin, and beneath it a slip of zinc or a cop- 
per coin. On touching the edges of the two metals so 
situated, we perceive a mild flash of light and 
a sharp prickling sensation or twinge, giving 
notice of the production of a voltaic current. 
This simple experiment was made long before 
the discoveries of Galvani and Volta, and is 
to be regarded as the first recorded observation 
in the remarkable science of galvanism. Volta 
accordingly arranged a series of copper and 
Bilver coins in a pile, with cloths wet in a 
saline or acid fluid between them. The ar- 
rangement is seen in fig. 152. The copper c 
and zinc z alternate with the wet cloth be- 

Pig. 152. 

tween. The pile begins with z and ends with c, and care 

What did he invent? 181. What reflection is here made ? 182. What 
was Volta'a reasoning ? What is tho simplest form of battery? 




must be taken that the order be strictly maintained, viz. 
copper — cloth — zinc. On establishing a metallic commuii* 
cation between these extremes (poles) by a wire, a current 
of electricity flows in the direction of the arrow on the wire. 
If orfe hand be placed on each end of the pile, a shock 
will be experienced, similar in some respects to that from 
the electrical, machine, and yet very unlike it. If the pile 
has many members, on touching the wires communicating 
between the extremes the shock is very intense, and a vivid 
spark will be produced, which is increased if points of pre- 
pared charcoal are attached to the ends of the wires. The 
conducting wires held together will grow hot, and if a short 
piece of small platina wire is interposed, it will be heated 
to bright redness. Such is an outline of the remarkable 
discovery of Volta, whose pile was made known to the 
world in 1800. The principle involved in this arrangement 
is unaltered, although more manageable and efficient forms 
of apparatus have supplied the place of the original pile. 

183. Simple Voltaic Circle. — A voltaic current is esta- 
blished whenever we bring two dissimilar metals (as copper, 
silver, or platina, with zinc or iron) into contact in an acid 
or saline fluid. Thus, if we place a slip of 
copper in a glass of acid water, and beside it 
in the same vessel a slip of amalgamated zinc, 
(fig. 153,) as long as the two metals do not 
touch there will be no action, but on bringing 
together the upper ends of the two slips of 
metal, a vigorous action will commence, bub- 
bles of gas will be rapidly given off" from the 
Fig. 153. copper, while the zinc will be gradually dis- 
solved in the acid water. This action will be arrested at 
any moment, on separating the two metals. If this separa- 
tion is made in the dark, a minute spark will also be seen. 
The action here is entirely electrical. The end of the* zinc 
in the acid is +, or positive, and that in the air — , or ne- 
gative ; the copper has the reverse signs. These relations 
are expressed in the figures by the signs -f- and — , and by 
the direction of the arrows showing the -f- electricity of the 
zinc passing to the — of the copper in the acid ; while the 
bubbles of gas (hydrogen) set free at the -J- end of the zino 

Describe the pile, fig. 152. 183. What axe the conditions of a voltaia 
circuit? How is its action suspended? What are the electrical states of 
the immersed metals ? Illustrate by figs. 153, 154. 





Fig. 154. 

are delivered at the — of the copper. Fig. 154 shows how 
the current may be established by wires, 
without the direct contact of the slips. In 
this case the wires (as in the pile) carry the i 
influence in the direction of the arrows, and 
the existence of the current and its positive 
and negative characters may be shown by 
the effect produced by it on a small mag- 
netic needle, which will be influenced by 
the wires carrying the current, just as by 
the magnet — being attracted or repelled 
according as it is above or below the wire, 
and in either case endeavoring to place itself at right angles 
to the conducting wire, (201.) The direction of the voltaic 
current (and of course the + or — qualities of the metals 
from which it is evolved) depends entirely on the nature of 
the chemical action produced. Thus, if, in the arrangement 
just described, strong ammonia were used in place of the 
dilute acid, all the relations of the metals and the fluid 
would be reversed, since the action would then be upon the 

184. Thus is electricity the result of chemical action; 
and conversely we see that, under the arrangement described, 
chemical action is controlled by the electrical condition of 
the metals. This is electricity in motion, or dynamic elec- 
tricity; and frictional electricity may be regarded as stag- 
nant or statical electricity. Let us attend somewhat further 
to the theory of the voltaic circle. 

185. In the compound voltaic circuit, composed of two 
or more members, connection is formed, not between members 
of the same cell, but between those of opposite names 
in contiguous cells. 
This is seen by in- 
specting the arrows 
and signs -f- and — 
in figure 155. The \ 
electricity always 
flows, both in simple 
and compound cir- 
cles, from the zinc 
to the copper, in the 

Fig. 155. 

184. How is this mode of electricity regarded ? 185. What are the con- 
ditions of a compound voltaic series ? Describe it in fig. 155. 




fluid of the battery; and from the copper to the zinc, oat 
of the battery. This is important to be remembered, since 
the zinc is called the electro-positive element of the voltaic 
series, although out of the fluid it is negative ; and conse- 
quently, in voltaic decomposition, that element which goes 
to the zinc-pole is called the electro-positive element, being 
attracted by its opposite force; while the element going 
to the copper is called, for the same reason, the electro- 
negative. The compound circle, reduced to the simplest 
form of expression, would be — 

Copper — zinc — -fluid— copper — zinc. 
Here the copper end is negative and the zinc positive, 
but the two terminal plates are in no way concerned in the 
effect ; so that, throwing them out of the question, we bring 
it to the state of the simple circle, which is simply — 

Zinc — fluid — copper ; 

and here we find the zinc end negative, and the copper end 

186. A certain resistance to the passage of a voltaic cir- 
cuit is offered by every element used in its construction. 
New properties are thus acquired by the compound circuit, 
which are never seen in the single couple, while the latter 
possesses certain attributes not seen so well in the compound 
series. For example, no single pair of plates, however large, 
will afford a current capable of decomposing water or of 
affording an electrical shock, although a maximum of mag- 
netic effect may thus be produced. These differences were 
formerly ascribed, rather vaguely, to what has been called 
quantity and intensity. Thus, in the compound circuit, 
supposing each -f- and — in the circuit to neutralize each 
other, then only the final quantities -f- and — remain as 
expressed in the poles; and it was argued that the quantity 
of electricity was no greater than would be afforded by a 
single couple, while its intensity, owing to the resistance over- 
come in each cell, was greatly increased. This matter has 
been placed on the basis of mathematical demonstration by 

187. Ohm's Law.— Ohm, of Berlin, in 1827 first de- 
monstrated that, as the voltaic apparatus itself is composed 

186. What effect is due to each element ? "What new properties does 
the current thus acquire? What was meant by quantity and intensity ? 
1S7. What law expresses the conditions of a voltaic circuit ? 




solely of conductors, the electric current must proceed, not 
only along the connecting wire, from pole to pole, but also 
through the whole apparatus ; that the resistance offered to 
the passage of the current consisted therefore of two parts, 
one exterior to, and one within, the apparatus. This expla- 
nation cleared up at once the difficulties which had previously 
beset this subject when regarded only in view of the exterior 

Let the ring a b c in fig. 156 represent a homo- a . 
geneous conductor, and let a source of electricity ^^^\ 
exist at A. From this source the electricity will / \ 

diffuse itself over both halves of the ring, the I J 

positive passing in the direction a, the negative x^_^/ 
in b, and both fluids meeting at c. Now it fol- . * 
lows, if the ring is homogeneous, that equal quan- **£• 156# 
tities of electricity pass through all cross sections of the 
ring in the same time. Assuming that the passage of the 
fluid from one cross section of the ring to another is due to 
the difference of electrical tension at these points, and that 
the quantity which passes is proportional to this difference 
of tension, the consequence is that the two fluids proceeding 
from A must decrease in tension the farther they recede 
from the starting point. 

188. This decreasing tension may be represented by a 
diagram. Suppose the ring in fig. 156 to be stretched out 
to the line A A'. Let the ordinate 
A B represent the tension of positive 
electricity at A, and A' B' that of the 
negative fluid; then the line BB' 
will express the tension for all parts 
of the circuit, by the varying lengths 
of A B, A' B' at every point of A c or FI * w " 

c A'. Hence Ohm's celebrated formula, F = ■?, where F 
represents the strength of the current, E the electro-motive 
force of the battery, and R the resistance. Therefore the 
greater the length of the circuit, the less will be the amount 
of electricity which passes through any cross section in a 
given time. In exact terms, this law states that the strength 

Demonstrate fig. 156. 188. How do you express the decreasing ten . 
lion ? What is Ohm's formula ? Give the meaning of each expression. 
What is the Ian as stated? 




of the current is inversely proportional to the resistance of the 
circuity and directly as the electro-motive force. 

189. Bat in the simplest voltaic circuit we have not a 
homogeneous conductor, but several of various powers in 

this respect. To illustrate this, let the 

conductor A A' (fig. 158) consist of 

two portions having different cross 

sections. For example, let the cross 

section of A d be n times that of d A! ; 

then if equal quantities pass through 

Pig. 158. all sections in equal times, if through 

a given length of the thicker wire no more fluid passes than 

through the thinner wire, the difference of tension at both 

ends of this unit of length of the thicker wire must be only 

-th of what it is in the latter. Thus, " the electric fall/' as 

w . . 

Ohm calls it, will be less in the case of the thick wire than 

of the thinner, as shown by the line B a in the figure. The 
result is expressed in the law that the " electric fall" is 
directly as the specific resistances of the conductors, and in- 
versely as their cross sections. Hence, the greater the resist- 
ance offered by the conductor, the greater the fall. The 
very simplest circuit must therefore present a series of gra- 
dients expressive of the tension of its various points — as 
one for the connecting wire, one for the zinc, one for the 
fluid, and one for the copper. The electro-motive force of 
a voltaic couple (" E" of Ohm's formula) may be experi- 
mentally determined, and it is proportional to the electric 
tension at the ends of the newly broken circuit. 

190. Galvanic Batteries are constructed of various forms, 
according to the purpose for which they are to be used. 

One of the earliest 

forms contrived was the 

Cruiekshank's trough, 

(fig. 159,) in which the 

plates of copper and 

lg * * zinc soldered together 

are secured in grooves by cement, water-tight, all the zincs 

facing in one direction. The acid was poured into the 

189. How does it apply to conductors not homogeneous ? What is the 
electric fall ? Give the law. Describe the course of tbe current in and 
out of the fluid. What is the simplest expression of the compound 
circle ? 190. What was Cruiekshank's battery ? 




trough until the cells were filled. To avoid the incon* 
veuience arising from loss of power, (which in this form of 
instrument is greatest at the first moment of contact be- 
tween the plates and the acid,) Dr. Hare contrived his 
revolving deflagrators. These were so constructed, that hy 
a quarter revolution of the trough, the acid could at plea- 
sure, and without disturbing the arrangements of the 
operator, be thrown off or on the plates, and the maximum 
effects of this kind of the battery be obtained. But 
recent improvements in the construction of the battery have 
supplied us with several superior forms of the instrument, 
suited to various purposes, and possessing the valuable qua- 
lity of constancy of action. 

191. Amalgamation, — In the original form of the gal- 
vanic battery, made of copper and of unamalgamated zinc, 
there is a great amount of local action in each cell, arising 
from the impurity of the zinc. When the surface of the 
sine is amalgamated with mercury, the local action ceases ; 
and the amalgamated surface, being reduced to one uniform 
electrical condition, will remain for any length of time in 
the acid fluid unacted on, until connected with the electro- 
negative element. All improved batteries are therefore now 
constructed with amalgamated zinc. It should be remarked 
that the heal action in a battery cell, arising from the 
cause named, not only consumes the power of that member, 
but reduces the energy of the whole series. In order to 
have a constant voltaic circuit of equal power, not only the 
evils arising from local action must be avoided, but also, as 
far as possible, the exhaustion of the fluid of excitation. 
Batteries so constructed as to meet these difficulties are 
called sustaining batteries, or constant batteries. Some of 
the more important of these we will briefly describe. 

192. Smee's Battery is formed of zinc and silver, and 
needs but one cell, and one fluid to excite it. The silver 
plate (S, fig. 160) is prepared by coating its surface with 
platinum, thrown down on it by a voltaic current, in the 
state of fine division, which is known as platinum-black. 
The object of this is to prevent the adhesion of the liberated 
hydrogen to the polished silver. Any polished smooth sur- 
face of metal will hold bubbles of gas with great obstinacy, 

What was Hare's improvement ? 191. What is amalgamation ? What 
its use ? What is said of local action ? 192. What is Smee's battery ? 



^ thus preventing in a measure the contact 

between the fluid and the plate by the in- 
terposition of a film of air-bubbles. The 
roughened surface produced from the de- 
posit of platinum-black entirely prevents 
this. The zinc plates z z in this battery 
arc well amalgamated, and face both sides 
of the silver. The three plates are held in 
position by a clamp at top b, and the 
interposition of a bar of dry wood w 
i prevents the passage of a current from 
plate to plate. Water, acidulated with 
one- seventh its bulk of oil of vitriol, or, 
for less activity, with one-sixteenth, is the 
exciting fluid. The quantity of electricity excited in this 
battery is very great, but the intensity is not so great as in 
those compound batteries to be described. This battery is 
perfectly constant, does not act until the poles are joined, 
and, without any attention, will maintain a uniform flow of 
power for days together. A plate of lead, well silvered, and 
then coated with platinum-black, will answer equally as 
well, and indeed better than a thin plate of pure silver 
This battery is recommended over every other for the stu- 

Fig. 160. 

Fig. 161. 

dent, as comprising the great requisites of cheapness, ease 
of management, and constancy. A form of it, well calcu- 
lated for the student's laboratory, is shown in fig. 161, 
which is a porcelain trough with six cells. This battery is 
the one universally employed in electro-metallurgy. ' 

193. DanieWs Constant Battery. — This truly philosophi- 
cal instrument (fig. 162) is made up of an exterior circular 

What are the advantages of Smee's battery ? 





Fig. 162. 

coll of copper C, three and a half inches in diameter, 
which serves both as a containing vessel and as 
a negative element ; a porous cylindrical cup 
of earthenware P (or the gullet of an ox tied 
into a bag) is placed within the copper cell, 
and a solid cylinder of amalgamated zinc Z 
within the porous cup. The outer cell C is 
charged by a mixture of eight parts of water 
and one of oil of vitriol, saturated with blue I 
vitriol, (sulphate of copper.) Some of the solid 
sulphate is also suspended on a perforated shelf, 
or in a gauze bag, to keep up the saturation. 
The inner cell is filled with the same acid | 
water, but without the copper salt. Any num- 
ber of cells so arranged are easily connected I 
together by binding screws, the C of one pair 
to the Z of the next, and so on. This instru- 
ment, when arranged "and charged as here described, will 
give out no gas. The hydrogen from the decomposed water 
is not given off in bubbles on the copper -side, as in all forms 
of the simple circuit of zinc and copper ; because the sulphate 
of copper there present is decomposed by the circuit, atom 
for atom, with the decomposed water, and the hydrogen 
takes the atom of oxyd of copper, appropriating its oxygen 
to form water agaiu, and metallic copper is deposited on 
the outer celL No action of any sort results in this battery, 
when properly arranged, until the poles are joined. Ten or 
twelve such cells form a very active, constant, and econo- 
mical battery. 

I94r. Iti the common sulphate of copper battery (fig. 163) 
only the acid solution of sulphate of copper is *\ 
used. The surface of zinc becomes soon en- 
cumbered by the metallic copper in a state of - 
fine division thrown down upon its surface. 
It is a very useful battery for electro-mag- 
netic purposes. 

195. Grove's Battery. — Mr. Grove, of Lon- 
don, has contrived a compound sustaining lg * 
battery, of great power and most remarkable intensity of 
action. The metals used are platinum and amalgamated 

193. What is Darnell's battery? 194. What is the sulphate of coppei 
battery ? What is Grove's battery ? 





Fig. 164. 

zinc. A vertical section of this battery is shown 
in fig. 164. The platinum -f- is placed in a 
porous cell of earthenware, containing strong 
nitric acid. This is surrounded by the amalga- 
mated zinc — in an outer vessel of dilute sul- 
phuric acid, (six to ten parts water to one of 
acid, by measure.) The platinum, being the 
most costly metal, is here surrounded by the 
zinc, in order to economize its surface as much 
as possible. In this battery the hydrogen of 
the decomposed water on the zinc side enters the 
nitric acid cell, decomposes an equivalent of the 
acid, forming water with one equivalent of its 
oxygen, while the deutoxyd of nitrogen is given out as a 
gas, and, coming in contact with the air, is converted into 
hyponitric acid fumes. No other form of battery can be com- 
pared with this for intensity of action. A scries of four 
cells (the platinum foil being only three inches long and 
half an inch wide) will decompose water with great rapidity; 
and twenty such cells will evolve a very splendid arch of 
light from points of prepared charcoal, and deflagrate all 
the metals very powerfully. It is rather costly, and trouble- 
some to manage, as are all batteries with double cells and 
porous cups. 

196. Bunsen-8 carbon batteiy is a valuable addition to our 
resources in this department. It employs a cylinder of car- 
bon for the negative element, in place of the 
platinum in Grove's battery. The carbon is 
] that of the gas-works, pulverized and mould- 
| ed with flour, and afterward baked like pot- 
| tery into compact cylinders. This battery 
(fig. 165) has the advantage of large mem- 
bers and great cheapness of construction. 
Fifty large-sized members, 10 inches high, 
the outer cups 5 inches in diameter, cost 
about fifty-five dollars in Paris, made by Deleuil, Rue du 
Pont-de-Lodi, No. 8. The author has found this, on the 
whole, the most efficient and economical of all batteries 
suited to show the more splendid and intense effects of 
voltaic electricity. 

Fig. 165. 

196. What is Bunsen's battery ? What is the reaction in these com- 
pound batteries ? 





197. The effects of voltaic electricity are, 
1. Physical; 2. Chemical; and, 3. Physio- 
logical. Under the first head are included 
the electrical, luminous, calorific, and elec- 
tro-magnetic phenomena of the circuit. 

198. Deflagration. — When the current 
from a series of 20 or 50 pairs of Grove's 
or Bunsen's battery is passed through 
points of prepared charcoal, as in the dis- 
charger, (fig. 166), a most brilliant light 
and intense heat are produced. No effect 
is seen until contact is made between the 
polesp and n, when, on withdrawing them, 
the arch of light elongates, and connects 
the separated poles, in 
the manner shown in 
fig. 167. This arch is 
in a powerful pile some 
inches in length. It is 
accompanied with an -™- , 
elongation of the pole "*■ 
on the — or carbon «*i«\ Fi * m 
side of the battery, and a depression or hollow- 
ing out of the -f- or zinc side. This flame is 
a conductor of electricity, and is attracted and 
repelled by the magnet, as shown in fig. 168. 
By holding a magnet in a certain position the 
flame may be made to revolve, accompanied 
at the same time with a loud sound. In the 
small capsule of carbon S, (fig. 169,) gold, 
platinum, steel, mercury, and other sub- 
stances are speedily fused and deflagrated, with 
various colored lights and volatilization. The 
easy fusion of platinum by the pile is a proof of 
the intensity of the heat, as this effect can be pro- 
duced by no other source of heat known, except 
that of the oxy hydrogen blowpipe. By the union 
of the currents from several hundred carbon cells, 
M. Despretz has lately volatilized the diamond. 
The ingenuity of the teacher will vary the ex- 
periments, always so surprising and instructive. 

Fig. 166. 

Fig. 169. 

Fig. 170. 

197. Classify the effects of voltaic electricity, 
oi deflagration. Which polo elongates ? 

198. Describe the effects 





199. The electrical light of the voltaic 
circuit is in no degree dependent on com- 
bustion, as may be proved by establishing 
connection between the poles in a vacuum 
in a glass vessel exhausted by the air-pump, 
and containing the poles conveniently ar- 
ranged, as in fig. 170. No less brilliancy 
is perceived in this case than in the air. 

200. A constant light is produced from 
the battery of Grove or Bunsen, by an in- 
genious mechanical arrangement of the 
poles. Fig. 171 shows that of M. Du- 
boscq, of Paris. The poles S and I are 
preserved at the same distance by the ac- 
tion of an electro-magnet in the foot E, 
upon a soft-iron bar F F in connection with 
an endless screw V, moving the pullies 
P P, which are connected by cords with 
the poles S and I. The contact of S and 
I induces magnetism in the electro-magnet 
E, while the springs E L regulate the mo- 
tion of the machinery* The apparatus is 
simple and portable, and its effect is to 
make the electrical light so steady and con- 
stant that it may be used for all optical ex- 
periments. The author has also shown 
that good daguerreotypes may be taken 
with it in a few seconds. For this pur- 
pose the light is concentrated by a large 
parabolic mirror, so placed that the poles 
meet in its focus. The positive pole con- 
sumes much more rapidly than the nega- 
tive, both from a more intense action upon 
it and because its particles are carried over 
and deposited on the negative pole, elon- 
gating the point of the latter. To provide for this difference! 
the pulley P is variable, and carries the pole I up propor- 
tionably faster, so that the focal position of the light remains 

Fig. 171. 

How does a magnet affect the are of flame ? 199. How does a vacuum 
affect the electrical light? Describe fig. 170. 200. What is the arrange- 
ment for rendering the light constant? Describe fig. 171. 




Ekctro-Magn etism* 

201. Prof. (Ersted, of Copenhagen, in 1819 first made 
known the law of electro-magnetic attraction and repulsion. 
If a wire conveying a voltaic current is brought above and 
parallel to a magnetic needle, (as shown in ' >■ 

fig. 172,) the latter is invariably affected, ^r 

as if influenced by the poles of another <c II - i n 
magnet If the current is flowing, as in- > 

dicated by the arrow on the wire, say to 
the north, then the north pole of the 
needle will turn to the east ; if the current _T**_t 

is flowing south, it will turn to the west. /*~^ 

If the wire carrying the current is placed Fl ** 172# 
beneath the needle, the same effect is produced as if the 
current had been reversed ; the needle turns in the opposite 
way to what it does when the wire is above. The effort of 
the needle is to place itself at right 
angles to the wire, as if influenced 
by a tangential force. That the wire 
conveying a voltaic current is itself 
magnetic, is proved by this experi- 
ment. If the wire is bent in a rect- 
angle, as in fig. 173, and wound with Fig. 173. 
silk or cotton, to prevent metallic contact, and the lateral 
passage of the power from wire to wire, then it is evident 
that a current flowing over the wire will 
have to pass many times completely 
around the needle, and the effect which 
is produced will be nearly in proportion 
to the number of turns made by the wire. 
In this way we can make a very feeble 
current give decided indications. Such 
an arrangement is called a galvanoscope 
or galvanometer. 

202. In delicate galvanoscopes, in order _________ 

to free the magnetic needle from the di- Fig. 174. 

rective tendency which it receives from 
the earth's magnetism, two needles are used, with their 
unlike poles placed opposite to each other, (fig. 174,) one 

201. Who discovered electro-magnetism ? What effect has a current on 
a wire ? What is meant bj a tangential force ? What is a galvanometer ? 





Fig. 175. 

within and the other above the coil. They will then hang 
suspended by the silk fibre which supports them, with no 
tendency to swing in any direction, since they are wholly 
occupied with their own attractions 
and repulsions, and their directive 
power is neutralized. Consequently, 
they are free to move with the slight- 
est influence of any current passing 
through the coil. Such an arrange- 
ment is called an astatic needle. To 
give it greater delicacy, and prevent 
the currents of air from moving it, 
a glass shade (fig. 175) is placed over 
it, and the movements of the needle 
are read on the graduated circle. By 
I means of a screw provided for that 
purpose, the coil is revolved until it is 
parallel with the needle, as the point 
of greatest sensitiveness. The ten- 
dency of the galvanometer needle, it will be remembered, 
is always to place itself at right angles to the direction of 
the electrical current, that position being the equator of the 
attracting and repelling powers, and consequently a point 
of equilibrium. 

203. Ampere's Theory. — In 1820, while the original dis- 
covery of OSrsted was attracting the greatest attention, M. 
Ampere, of Paris, proposed to account for the phenomena 
of terrestrial magnetism by supposing a series of electrical 
currents circulating about the earth from east to west, in 
spirals nearly at right angles to its magnetic axis. The 
sun's rays impinging on the surface of the earth, encircle it, 
so to speak, with an unending series of spiral lines, pro- 
ducing, by thermo-electricity, the phenomena of magnetic in- 
duction. Arago found, in accordance with these views, 
that if iron-filings were brought near a connecting wire 
while a voltaic current was passing, that they adhered to it 
in concentric rings. These fell off the moment the circuit 
was broken. Hence it was inferred that if a voltaic current 
was made to pass in a spiral about any conductor/ it would 
become magnetic. This inference was verified by the 

202. What is an astatic needle ? How is it freed from the influence 
of terrestrial magnetism ? 203. What was Ampere's theory ? What de- 
monstration did M. Arago devise? 





Fig. 176. 

204. Edix. — A wire coiled as in fig. 176, made the me- 
dium of communication for a voltaic current, becomes ca- 
pable of manifesting very strong 
magnetic influence on any con- 
ductor placed in its axis. A 
delicate steel needle, laid in the 
helix, will be drawn to the 
centre and held suspended there, 
without material support, like 
Mahomet's fabled coffin. If the needle is of steel, the mag- 
netism it thus receives will be retained by it ; but if it be 
of soft iron, it is a magnet only while the current is passing 
Brass, lead, copper, or any other metallic conductor, can by 
galvanism be made to manifest temporary magnetic power. 
The polarity of the needle in the helix will depend on the di- 
rection in which the current is carried; if from right to left, the 
south pole will be at the zinc end ; if from left to right, this 
polarity is reversed. If the spiral is reversed in the middle, 
then a pair of poles will be found at the 
point of reversal, and this as often as the £ 
reversal may happen. A steel needle placed J> 
in such a helix receives the same reversals. J 1 
Such an arrangement is shown in fig. 177. 4 

205. The polarity of the helix is well 
shown by the arrangement represented in 
fig. 178, called De la Rive's ring. A small 
wire helix, whose ends are attached to the 
little battery of zinc and copper con- 
tained in a glass tube, floats on the 
surface of a basin of water, by means 
of a large cork, through which the 
glass tube is thrust. On exciting 
this small battery by a little dilute 
acid, poured into the tube, and 
placing the apparatus on the water, 
it will at once assume a polar direc- F . 178 
tion, as if it were a compass-needle, 

the axis of the helix being in the magnetic meridian ; and 
it will then obey the influence of any other magnet brought 
near it, manifesting the ordinary attractions and repulsions 

204. What is the helix? How is a needle in it affected? What po- 
larity has it ? What does fig. 177 illustrate ? Why are the poles reversed 
at N ? 205. What shows the polarity of the wire itself? Describe fig. 17S. 

Pig. 177. 





Fig. 179. 

206. The helix is placed as in figure 
179, its lower end dipping into a cup 
of mercury p, in connection with one 
pole k f while it is held by its upper 
end n in connection with the other 
pole. In this situation, when the cur- 
rent passes, the separate turns of the 
\ helix attract each other, thus shorten- 
i ing the spiral and raising the point out 
(of the mercury, with a vivid spark. 
This breaks the connection — the un- 
magnetized helix falls — the point again 
touches the mercury, when a fresh contraction happens. 
These effects are made very striking by holding one end of 
an iron rod, or of a bar magnet, within the spiral. If a 
magnetic bar is used, the vibrations obey the ordinary law 
of polarity, ceasing entirely when a pole of like name is 

207. Electro-Magnets. — The induction of magnetism in 
soft iron by the voltaic current, furnishes us the means 

of producing magnets of astonishing power. 
Let a b (fig. 180) be a cylinder of soft iron, 
fitting the opening of a helix. If the cur- 
rent from several Grove's batteries be passed 
through the wires mn, sufficient magnetic 
power will be developed to sustain a 6, oscil- 
I lating in a vertical line, even should it weigh 
eight or ten pounds. This is one of the most 
surprising of all experimental demonstrations. 
By the use of this arrangement on a large 
scale, and with a battery of 100 members of platina, a foot 
square, Dr. Page sustained a mass of soft iron 600 pounds 
in weight, with a vertical movement of eighteen inches. 
On this principle he has propelled a magnetic engine on a 
railway at considerable speed, and sought to apply the power 
to other mechanical uses. 

208. Professor Henry first demonstrated the fact that the 
power of an electro-magnet with a given voltaic current 
was greatly increased when the helix wire was divided into 

Fig. 180. 

206. Explain the action of the helix in fig. 179. 207. What is an electro- 
magnet? What remarkable result is mentioned? 208. What did Pro- 
fessor Henry first show ? 





eoife of limited length. Availing himself 
of this principle, he constructed electro- 
magnets lifting over two thousand pounds, 
with a single cylinder hattery of small 
sice. All the corresponding ends of the 
helices are carried to their appropriate 

209. The ring helix (fig. 182) is a 
striking mode of exhibiting the inducing 
effect of a voltaic current. Here two 
semicircles of soft iron, fitted with han- 
dles, are magnetized by the current 
passing in R, the ends ah being in con- 
nection with a battery. The rings of iron 
and of wire are quite separate, and, when 
the current passes, the iron (about f inch 
diameter) becomes so strongly magnetic 
as to sustain, easily, 50 pounds. Small 
electro-magnets have been made to sustain 
420 times their own weight. 

210. Electro-magnetic Motions. — Faraday 
first produced motion by the mutual action 
of magnets and conductors, and Prof. Hen- 
ry, in this country, about the same time. 
By various combinations of the principles 
already explained, a great number of inge- 
nious pieces of electro-magnetic apparatus 
have been contrived for showing motion ; by 
wires attracting and repelling — by circles 
and rectangles of wires revolving the one 
within the other — by armatures revolving 
before the poles of permanent or electro- 
magnets, and these adapted to carry various 
forms of machinery. But as these illus- 
trate no new principles, we refer the student 
to the excellent manual of magnetism by 
Daniel Davis, Boston, where the whole 
subject will be found very ably discussed. 
211. The Electro-magnetic Telegraph is 

Fig. 181. 

Fig. 182. 
a contrivance 

which very happily illustrates the application of abstract 

209. What does fig. 182 show? 210. Who first observed electro-mag- 
netic motions? 





scientific principles and discovery to the wants of society. 
The inconceivably rapid passage of an electrical current over 
a metallic conductor was discovered by Watson in 1747^and 
this discovery gave the first hint of the possibility of using 
electricity as a means of telegraphic communication. Nume- 
rous attempts were made, very early after this discovery, to 
construct a telegraph to be worked by ordinary electricity ; but 
from difficulties inherent in the mode, these attempts were 
attended with only very partial success. The discovery of 
electro-magnetism by CErsted, in 1820, supplied the neces- 
sary means of successful construction. Superior to all other 
contrivances in the essential conditions of simplicity, in con- 
struction and notation, is the beautiful contrivance patented by 
Professor Morse in 1837. In the accompanying figure (183) 

Fig. 183. 

we have a view of the most essential parts of Morse's tele- 
graphic register. A simple electro-magnet m m, with its 
poles upward, receives its induced magnetism from a cur- 
rent of electricity conducted by the wires W W from the 
distant station. As soon as the circuit is completed, m m 
becomes a magnet, and draws to its poles an armature or bar 
of soft iron a on the lever I. The motion of this lever starts 
a spring which sets in motion the clock arrangement c. This 
clock machinery, in consequence of the weight attached to 

211. Explain the principles oi' the electro-magnetic telegraph and itf 




ft, will, when once set in motion, continue to move. The 
immediate object of the clock machinery is to draw forward 
a narrow ribbon of paper pp in the direction of the arrows, 
and to cause it to advance with a regular motion. The paper 
ribbon passes by the end of the pen-lever l } in which re a 
steel point *, that indents the paper whenever this end of 
the lever is thrown upward by the attraction of the armature 
a to the magnet m. If m m were constantly magnetized, 
the mark made by the point s would be a continuous line. 
But we can make and discharge an electro-magnet as often 
and as fast as we please ; the instant, therefore, the circuit 
WW is broken, m m ceases to be a magnet, and lets go the 
iron armature a, when the point s of the lever falls, so as 
no longer to mark the paper. The circuit being renewed, 
the point marks again ; and this may be repeated as often 
as the operator pleases. The length of time that the circuit 
is closed will be exactly registered in the corresponding 
length of the mark made by *. The completing of the cir- 
cuit is performed by touching a spring on the operator'* 
table, which establishes a metallic communication between 
the poles of the battery. A touch will produce a dot, a con- 
tinued pressure a long line, and intermitting repeated touches 
a series of dots and short lines. These easily form an alpha- 
bet. . To complete the arrangement, each operator must have 
his own battery in connection with the register at the dis- 
tant station. In practice, only one wire is used with each 
register, the circuit being completed by connecting the other 
pole of the battery with the moist earth by means of a buried 
metallic plate and a wire. The remarkable observation that 
the earth could be used in this manner as a part of the cir- 
cuit, was made by Steinheil, in Germany, in 1837. Such is 
a brief account of one of the most remarkable discoveries of 
modern times. In Bain's telegraph, the circuit decomposes 
a salt of iron, staining a paper with the marks of the con- 
ductor, and no magnet is employed. 

212. The telegraph has become an important auxiliary in 
astronomical observations, by furnishing an exact means of 
determining longitudes. For this purpose the principal 
astronomical observatories in the United States are connected 
by telegraphic wires, and such is the velocity of the electrical 
wave that any communication made from one station will be 

2& How is the telegraph auxiliary to astronomy? 

Digitized by LiOOQ iC 


received at all the others at almost the same instant. The 
velocity of the wave has been determined by the experiments 
of the Coast Survey to be about 15,000 miles in a minute. 
Wheatstone asserts that the wave of electricity moves as 
rapidly at least as that of light. Other very ingenious and 
important applications have been made of the telegraph for 
regulating time-pieces and for signalizing fires. The city 
of Boston is provided with such a system, a detailed descrip- 
tion of which may be found in the American Journal of 
Science for January, 1852. 

One curious fact connected with the operation of the tele- 
graph is the induction of atmospheric electricity upon tho 
wires to such an extent as often to cause the machines at the 
several stations to record the approach of a thunder-storm. 
This induction occasions a serious inconvenience in working 
the telegraph, not unattended with danger to the operators. 
213. Professor Henry observed that when the current 
from a single pair of plates was passed through a long con- 
ducting wire, a vivid spark appeared at the instant of 
breaking contact between the conductor and the battery ; 
accompanied, also, by a feeble shock. A long conductor, 
then, supplies the place of an increased number of plates in 
a voltaic scries, and to some degree imparts the quality of 
intensity to a current of quantity. A flat spiral of copper 
ribbon, one hundred feet long, wound with cotton, and var- 
nished, shows these effects well. 
The magnetic needle indicates the 
direction of the current, (fig. 184.) 
The opposite sides of the spiral of 
course produce opposite effects on 
the needle. The magnetism pro- 
| duced is, however, to be distin- 
guished from the new effects ex- 
cited by the passage of the feeble 
Fie. 184. current through the coiled con- 

ductor, on breaking contact, t. e. 
the vivid spark and the shock. The latter is feeble with 
100 feet of copper ribbon, and becomes more intense if tho 
length of the conductor be increased, the battery remaining 
the same ; but the sparks are diminished by lengthening 

What other facts are mentioned regarding the telegraph J 213. What 
was Henry's observation on the spiral ? 





the conductor beyond a certain point. The increase of in* 
tensity in the shock is also limited by the increased resistance 
or diminished conduction of the wire, which finally counter- 
acts the influence of the increasing length of the current 
On the other hand, if the battery power be increased, the 
coil remaining the same, these actions diminish. 

214. These effects Prof. Henry ascribed to the generation 
of a secondary current at the moment of breaking contact. 
This secondary current moves in a direction opposite to that 
of the battery current. If a long coil of fine, insulated wire 
be brought within a small distance of the flat spiral, this 
new current will be detected in the second coil. The ar- 
rangement used by Prof. Henry is seen in the annexed figure. 
A small battery L is connected with the flat spiral of copper 
ribbon A by wires from the battery cups Z and C. This 
communication is broken at will, by drawing the end of one 
of the battery wires Z over the rasp. When the coil of fine 
wire W is in the position indicated in fig. 185, and the hands 

Fig. 185. 

grasp the conductors, a violent shock is felt as often as the 
circuit is broken by the passage of the wire over the rasp. 
When the coil W contains several thousand feet of wire, and 
is brought near A, the shocks are too intense to be borne. 
As this induction takes place through a distance of many 
inches, we can, by placing the spiral A against a division 
wall, or the door of a room, give shocks to a person in 
another room, who grasps the conductors of the wire coil W, 
and brings it near to the wall on the side opposite to A. A 
screen or disc of metal introduced between the two coils will 
cut off this inductive influence. But if it be slit by a cut 

214. What were these currents called? How do they move? What 
•f the spark and shock ? 





from the centre to the circumference, as a ft 
i in fig. 186 ; the induction of an intense current 
in W is the same as if no screen were present. 
Fig. 186. Discs or screens of wood, glass, paper, or other 
non-conductors, offer no impediment to this induction. 

215. Induced Currents of the third, fourth, and fifth order. 
— If the wires from W be connected with another flat spiral, 
and it with a second coil of fine wire, and so on, (fig. 187,) 
a series of currents will be induced in each alternation of 
coils. The secondary intense current in B will induce a 
quantity current in the second flat spiral C ; and a second 
fine wire coil W will induce a tertiary intense current, and 
so on. These currents have been carried to the ninth order, 

Fig. 187. 

decreasing each time in energy by every removal from the 
original battery current. The polarity, or direction of these 
secondary currents, alternates, commencing with the second- 
ary. Thus the current of the battery is -(- J ana * the secondary 
current is + 5 the current of the third order is — ; the cur- 
rent of the fourth order is + > and the current of the fifth 
order is — . These alternations are marked in the figure 
above, and were also determined by Prof. Henry. 

216. Compound Electro-magnetic Machine. — By combin- 
ing the results just briefly enumerated, a great number of 
ingenious electro-magnetic machines have been produced, 
adapted to medical use, and illustrative of the induction of 
magnetism and secondary currents. One of these, contrived 
by Dr. Page, is seen in fig. 188. In this little machine, a 
short coil of stout insulated copper wire forms a helix, within 
which some straight soft-iron wires M are placed. The 

215. To what degree have they been carried? 





battery current is 
made to pass through 
this stout wire, by 
which means mag- 
netism is induced in 
the soft iron. The 
conducting wires are 
so arranged beneath 
the board that the 
glass cup C contain- 
ing some mercury is 

Fig. 188. 

in connection with the battery. The bent wire W dips into 
this mercury, and also by a branch into B, and when in the 
position shown in the figure, the current from the battery 
will flow uninterruptedly. As soon, however, as the battery 
connection is completed, M becomes strongly magnetic, and 
draws to itself a small ball of iron on the end of P; this 
moves the whole wire P W and raises the point out of the 
mercury C; as the wire leaves the mercury, a brilliant 
spark is seen on its surface, the contact being thus broken 
with the battery, M ceases to receive induced magnetism, 
and the ball P being consequently no longer attracted to 
M, the wire W falls by its gravity to the position in the 
figure. This again establishes the battery connection, and 
the same effects just described recur; thus the bent wire W 
receives a vibratory motion, and at each vibration a brilliant 
spark is seen at C, and M becomes magnetic. It remains 
only to mention that the short quantity wire is surrounded 
by a fine intensity wire, 2000 to 3000 feet long, having no 
metallic connection with the battery or quantity wire, with 
its ends terminating in two binding screws on the left of 
the board. The fine wire receives a secondary induced cur- 
rent like the coil W, (185,) which, if touched, produces the 
most intense shocks at each vibration of the wire. These 
shocks are graduated by withdrawing part or all of the soft- 
iron wires M. 

217. Magneto-Electricity. — As we have seen effects pro- 
duced from galvanism which exactly resemble those of ordi- 
nary machine electricity and the magnetic influence, so, 
conversely, we might expect the production of electrical 
effects from the magnet. The electrical current from a single 

216. Explain the apparatus, fig. 188. 





galvanic pair, w.e have seen, produces magnetism in a spiral 
wire at right angles with its own course ; so the induction 
of magnetism in soft iron from a permanent magnet, in like 
manner, produces an electrical current at right angles to 
itself in the wire coiled on the armature. This class of 
phenomena was discovered by Faraday in 1831, and our 
countryman, Mr. J. Saxton, soon contrived a machine very 
similar to the one in fig. 189, called a magneto-electrical 

Fig. 189. 

machine. This consists of a powerful magnet S, secured to 
a board, with its poles so situated that an armature, formed 
of two large bundles of insulated copper wire W, wound on 
soft-iron axes, may be revolved on an axis before its poles, 
by the multiplying wheel M. A current of electricity is 
thus induced in W, just as in the flat coils, the permanent 
magnet here taking the place of the flat spiral. The cur- 
rent excited in W is led off by conductors to the binding 
screws p and n, the continuity of the current being broken 
/^ ~£^ (in imitation of the rasp in 185) by a contrivance 
f * pm at b on the axis, called a break-piece, (fig. 190,) 
VI z J which is made by alternate ribs of metal c and 

^11 ' ivory t, the current is broken by the ivory and 

Fig. 190. renewed by the metal, and at every break, the 
person whose hands grasp the conductors, secured to p 
and n, feels a sharp shock, which may be graduated at 
will by the rapidity of the revolutions of M, and by the 
adjustment of the break b. A long and fine wire — say 

217. What is magneto-electricity ? Explain fig. 189. 




8000 feet of wire ^ of an : z*Sn in diameter — is required 
to produce shocks and chemical decompositions. A shorter 
and stouter wire, as 250 feet of wire y 1 ^ or J$ inch in dia- 
meter will produce no shock, but will deflagrate the metals 
powerfully, and produce a secondary current of induction 
in soft iron. We thus imitate in magnetism the effects 
produced from a voltaic current, the short and stout 
wire of the armature is the simple circuit of large plates; 
the long and fine wire is like the compound circuit of smaller 

Thermo-Electricity, or the Electrical Current excited 
by Heat. 

218. If two metals unlike in crystalline structure and 
conducting power are united by solder, and the point of 
their union is heated or cooled, an electrical 
current will be excited, which will flow from 
the heated point to the metal which is the 
poorer conductor. Bismuth and antimony are 
such metals, being bad conductors, and unlike 
in crystalline structure. If two bars of these 
metals are united, as in fig. 191, and the point 
c is warmed by a lamp, a current will be set Fig. 191. 
in motion, which will flow from b to a, as in the figure. 
The compass- needle may be thus 
affected, as by the voltaic current. 
For this purpose two bars may be 
mounted as in fig. 192, and their 
junction being heated by a lamp, 
the needle will swing, in conse- 
quence of the electrical current 
excited by the heat. When several Fig. 192. 
such are joined, we have a greatly increased 
effect, as in the thermo-electric pile in Melloni's 
apparatus, (fig. 193.) 

219. Thermo-electric effects are not confined 
to metals, for they may be produced from other * lg# 193, '' 
solids, and even from fluids j and a single metal, as an iron 
wire, which has been twisted or bent abruptly, will originate 
a thermo-electric current when the distorted part is greatly 

218. What is thermo-electricity ? How doe* the current move ? 

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heated. The rank of the principal metals in the thermo- 
electric series is as follows, beginning with the positive : — 
Bismuth, mercury, platinum, tin, lead, gold, silver, zinc, 
iron, antimony. When the junction of any pair of these is 
heated, the current passes from that which is highest to that 
which is lowest in the list, the extremes affording the most 
powerful combination. 

If we pass a feeble current of electricity through a pair 
of antimony and bismuth, the temperature of the system 
rises, if the current passes from the former to the latter ; 
but if from the bismuth to the antimony, cold is produced 
in the compound bar. If the reduction of temperature is 
slightly aided artificially, water contained in a cavity in one 
of the bars may be frozen. Thus we see that as change of 
temperature disturbs the electrical equilibrium, so conversely 
the disturbance of the latter produces the former. 

Animal Electricity. 

220. The existence of free electricity in the animal body 
is proved by the results of Aldiui and Matteucci. In some 

animals we see a special apparatus 
for the purpose of exciting at will 
intense currents of electricity. 
There are also such currents in all 
animals. For example, when the 
lumbar nerves of a frog, held in 
the manner shown in fig. 194, are 
touched to the tongue of an ox 
lately killed, and at the same in- 
stant the operator grasps with the 
Mother hand, well wetted in salt 
T water, an ear of the ox, a con- 
vulsion of the frog's legs indicates 
Fig. 194. the passage of an electric current. 

221. The same delicate electroscope also shows similar 
excitement when its pendulous ischiatic nerves touch the 
human tongue, the toe of the frog being held between the 

219. What range have these effects ? How is a fall of temperature ob- 
served in a compound bar of antimony and bismuth ? 220. What is 
animal electricity ? Explain the experiment in fig. 194. 221. How else 
is the same fact shown ? How does the cunont oiroulate ? 




moistened thumb and finger of the experimenter. This is 
what Donne* calls the musculocutaneous current; passing 
from the external, or cutaneous, to the internal, or mucous, 
covering of the body. This current may be de- 
tected, as was shown by Aldini, in the frog's 
legs above. For this purpose he prepared the 
lower extremities of a vigorous frog, (fig. 195,) { 
and, by bending up the leg, brought the muscles 
of the thigh in contact with the lumbar nerves : 
contractions immediately ensued. Thus it ap- 
pears from experiments made by Matteucci, that 
a current of positive electricity is always circu- 
lating from the interior to the exterior of a 
muscle, and that although the quantity is ex- Flg * 1W * 
ceedingly small, yet by arranging a series of muscles, having 
their exterior and interior surfaces alternately connected, 
he produced sufficient elec- 
tricity to cause decided 

effects. By a series of half ^< 
thighs of frogs, arranged as \ 
in fig. 196, he decomposed Fig. 196. 

the iodid of potassium, deflected a galvanometer needle to 
90°, and by a condenser caused the gold-leaves of an elec- 
troscope to diverge. The irritable muscles of the 
frog's legs form an electroscope 56,000 times more 
delicate than the most delicate gold-leaf electro- 
nic fcei\ Professor Matteucci's frog-galvanoscope 
(fig. 197) is therefore far the most sensitive test 
of electricity that can be employed. When the 
pendulous nerve is touched simultaneously in the 
places where electrical excitement is suspected, 
the muscles in the tube are instantly convulsed. 

222. The electrical eel of South America men- 
tioned by Humboldt, and the torpedo — a flat fish 
found on our own coast — are remarkable examples g# 197, 
of those animals having a special electrical apparatus of 
nervous matter and cellular tissue arranged in the manner 
of the pile. The student is referred to the lectures of Pro- 

What has Donne called it ? How is it shown in the legs of the frog 
alone ? How does this current circulate ? How does fig. 196 prove it ? 
What is the delicacy of the frog-galvanoscope ? 222. What animals have 
a special electric apparatus ? 




feasor Matteucoi on living beings for further details on this 
very interesting subject. We can only add, that the shock 
from these animals is sufficient to charge a Leyden jar, to 
produce chemical decompositions, and to paralyze vigorous 

The legs of the common grasshopper are, it is said, 
equally sensitive electroscopes as those of the frog. 

Electro- Chemical Decomposition. 

223. By far the most interesting chemical result of 
Volta's pile was the new power it placed in the hands of 
chemists, of unfolding the secrets of combination, and of 
assigning their relative positions to the several elements. 
Indeed, the electro-chemical theory has been carried so far 
by some chemists, that every chemical decomposition has 
been referred to the play of electrical forces. 

224. The decomposition of water is the finest possible 
illustration of this power. Water is a compound of oxygen 
and hydrogen gases, in the proportions of one measure of 
the former to two of the latter. When two gold or platinum 
wires are connected with the opposite ends of the battery, 

and held a short distance asunder in a cup 
of water, a train of gas-bubbles will be seen 
rising from each and escaping at the surface. 
With two glass tubes placed over the plati- 
num poles, (fig. 198,) we can collect these 
bubbles as they rise, and shall soon find that 
the gas given off from the — plate is twice 
the volume of that obtained from the + 
plate. When the tubes are of the same size, 
this difference of volume becomes at once evi- 
dent to the eye. By examining these gases, 
we shall find them, respectively, pure hydro- 
Fig. 198. g en an( j p Ure oxygen, in the exact proportion 
of two volumes of the former to one of the latter. The 
rapidity of the decomposition is greater when the water 
is made a better conductor, by adding a few drops of 
sulphuric acid. 

223. What was the most interesting result of Volta's pile ? 224. Ho# 
is water decomposed by it? Describe fig. 198. 





If we employ a decomposing cell with 
only one tube over the conductors, it will 
be found that the gaseous contents will 
explode by the electric spark or by a 
lighted taper ; and if this is done over 
water the perfection of the vacuum re- 
sulting from the explosion will be seen 
by the height of the column which rises 
in the tube, (fig. 199.) 

225. We learn from this most in- 
structive experiment, that the voltaic 
current has power to decompose chemi- 
cal compounds, that this decomposition 
takes place in definite proportions of 
the constituents — and that these consti- 
tuents appear invariably at opposite 
poles of the battery. Fig. 199. 

226. A decomposing cell interposed in the circuit will 
give ub an esact account of the amount 
of electricity flowing. Such an in- 
strument has been called by Faraday 
a voltameter^ (fig. 200.) It differs 
from the common decomposing cell, 
in having a ground-glass tube at top 
bent twice, no as to deliver the accu- 
mulating gases into a graduated air- 
vessel, in which their volume is mea- 
sured, A more simple form of the 
apparatus is easily constructed, as in 
figure 201, (page 144,) of two glass 
tubes, two corks, and the conductors p p. 

227. The experimental researches in electricity by Dr. 
Faraday wbiob are the basis of modern science on 
this subject, required the introduction of certain new 
terms, some of which require explanation. The termi- 
nal wires or conductors of a battery are often termed 
the poles, as if they possessed some attractive power by 
which they draw bodies to themselves, as a magnet attracts 
iron. Faraday has shown that this notion is a mistake, 
and that the terminal wires act merely as a path or door 

225. What does this experiment teach? 226. What other cells are 
named ? 227. What is said of Faraday's researches ? What did they re- 
quire? What does he call the poles, and why? 

Fig. 200. 




PQ to the currents, and he therefore calls them 

electrodes, from electron and odos, a way. 
The electrodes are any surfaces which convey 
' an electric current into and out of a decom- 
posable liquid. The term electrolysis, from 
electron, and the Greek verb luo, to unloose, 
is used to express decomposition ; and the 
substances suffering decomposition are termed 
electrolytes. Thus, the experiment mentioned 
in the last section is a case of electrolysis, in 
which water is the electrolyte. The elements 
of an electrolyte are called ions, from the 
. Jj Greek particle ion, going, since the elements 

I <?o to the -f- or — electrode. The electrodes are 

"^ ^ distinguished as the anode and the cathode, 

from ana, upward, and odos, way, or the way 
PO in which the sun rises ; and kata, downward, 

Pig. 201. and odos, or the way in which the sun sets ; 
the anode is -{-, and the cathode — . We will now briefly 
consider the 

228. Conditions of Electro- Chemical Decomposition. — 
(1.) All compounds are not electrolytes, that is, they are 
not directly decomposable by the voltaic current. Many 
bodies, however, not themselves electrolytes, are decomposed 
by a secondary action. Thus, nitric acid is decomposed in 
the electrical circuit by the secondary action of the nas- 
cent hydrogen, which, uniting with one equivalent of the 
oxygen, again forms water and nitrous acid. Sulphuric 
acid is not an electrolyte, while hydrochloric acid is ; and 
the nascent chlorine from the latter attacks the -|- electrode, 
if it be of gold. (2.) Electrolysis cannot happen unless 
the fluid be a conductor of electricity ; and no solid body, 
however good a conductor, has ever been thus decomposed. 
A plate of ice, however thin, interposed between the elec- 
trodes, will entirely prevent the passage of the power ; but 
the electrolysis will proceed as soon as the least hole melts 
in the ice, through which the power can pass. Fluidity is 
therefore a very essential condition of electrolysis. The 
fluidity may be that of heat, or of solution; thus, the 

- Explain the terms electrode! electrolysis, and electrolyte. What are 
ions ? 228. Are all compounds electrolytes ? Give examples. What 
is the second condition of electrolysis ? Give examples. 




chlorids of lead, silver, and tin are not electrolysed in a 
solid state, but when fused they are decomposed with ease. 
(3.) The ease of electro-chemical decomposition seems in 
a good degree propoitioned to the conducting power of the 
fluid. Thus, pure water is by no means a good conductor, 
and its electrolysis is difficult ; but the addition to it of a 
few drops of sulphuric acid, or of some other soluble con- 
ductor, greatly promotes the ease with which it is decom- 
posed. (4.) The amount of electrolysis is directly propor- 
tioned to the quantity of electricity which passes the elec- 
trodes. (5.) The binary compounds of the elements, as 
a class, are the best electrolytes. Water and iodid of 
potassium are instances; while sulphuric acid, which has 
three equivalents of base to one of acid, is not an electro- 
lyte. No two elements seem capable of forming more than 
one electrolyte. (6.) Most of the salts are resolvable into 
acid and base. Thus, sulphate of soda is resolved into sul- 
phuric acid, which appears at the + electrode, and will 
there redden a vegetable blue; and the soda which appears 
at the — electrode will restore the previously reddened 
blue; so that by reversing the direction of the current, 
these striking effects are also reversed. 

229. (7.) A single ton, as bromine, for instance, has no 
disposition to pass to either of the electrodes, and the cur- 
rent has no effect upon it. There can ' be no electrolysis 
except when a separation of ions takes place, and the se- 
parated elements go one to each electrode. (8.) There 
is no such thing, in fact, (as has been often supposed,) 
as an actual transfer of ions from one part of the fluid to 
cither electrode. In the case of water, for example, oxygen 
is given out on one side, and hydrogen on the other. In 
order that this may be the case, there must be water be- 
tween the electrodes. We cannot believe that the separa- 
tion of the elements takes place 
at the electrode where one ele- 
ment is evolved, and that the 
other travels over unseen to the 
opposite electrode. We may, p . 202 

(3.) To what is the ease of the electrolysis proportioned ? (4.) Tc 
what is its amount owing ? (5.) What class of compounds are the best 
electrolytes ? Give examples. (6.) What of salts ? Give examples. 
229. (7.) What is said of a single ion? (8.) What of the transfer of 
ions ? Give the explanation offered of the decomposition of water. 




however, conceive of water in its quiet state, as represented 
by the diagram, (fig. 202,) each molecule being firmly 
united by polar attractions (218) to every other, and that 
the electrolytic force of the electric current has power to 
disturb this polar equilibrium, each molecule being simi* 
larly affected. In this case the electrolysis will proceed 
from particle to particle through the whole chain of affini- 
ties, decomposing and recomposing, until the ultimate parti- 
cle on each side, having no 





polar force to neutralize 
that eleo- 

XXX XX X r\ ' xt > esca P es at that ele °- 

^^J^J^J^Mo® trode which has a p° larifc y 

F 2os opposite to itself. This 

lg * " explanation may be better 

understood, perhaps, by inspecting the second diagram, (fig. 
203,) which represents a series of compound molecules of 
water undergoing electrolysis, the H and being eliminated 
at the opposite extremities. The same explanation will be 
found to serve for all other cases of electrolysis, both simple 
and secondary. 

230. (9.) A surface of water, and even of air, has been 
shown capable of acting as an electrode, proving that the 
contact of a metallic conductor with the decomposing fluid 
is not essential. The discharge from a powerful electrical 
machine was made to pass from a sharp point through 
air to a pointed piece of litmus paper moistened with sul- 
phate of soda, and then to a second piece of turmeric paper 
similarly moistened. This discharge had power to effect a 
true electrolysis ; the blue litmus was reddened by the sul- 
phuric acid set free from the sulphate of soda, while the 
yellow turmeric was turned brown by the alkaline soda from 
the same salt. 

231. (10.) Electrolysis takes place in a series of com* 
pounds in the precise order of their equivalents. Thus, if 
wine-glasses are arranged in a series, and in one is placed 
sulphate of soda, in another acidulated water, in another 
iodid of potassium, and in another hydrochloric acid, and if 
the whole series be connected together by siphon tubes, or 
moistened lampwick, passing from glass to glass, and a 

230. (9.) What is said of electrolysis without metallic conductors? 
Explain the experiment of the electrolysis of sulphate of soda by the 
electrical machine 231. How does electrolysis occur in a series of com- 




powerful galvanic current be then passed through them, 
electrolysis will occur in all, but unequally. 

It has been proved by acccurate experiment, that the 
decomposition which ensues is in exact proportion to the 
equivalents of each substance. In other words, we may say 
it requires one equivalent of electricity to decompose one 
equivalent of an electrolyte formed from the union of an 
equivalent of acid and another of base. Conversely, from 
the fact that an equivalent of electricity is required to de- 
compose any compound, it is proved that the opposite ele- 
ments of this compound, in uniting, will disengage the same 
equivalent of electricity. 

232. (11.) The passage of a current within the cells of a 
voltaic battery depends also upon the decomposition in each 
cell, equally with that between the platinum electrodes. 
The same phenomena which we notice in the decomposing 
cell (224) take place also in each battery cell. Water is 
decomposed, and the hydrogen is given off from the positive 
plate, while the oxygen combines with the zinc, and thus 
escapes detection. Therefore, no fluid not an electrolyte is 
suitable to excite a battery. Acid water acts, for this pur- 
pose, only by the decomposition of the water and oxydation ' 
of the zinc. The presence of the acid is useful only so far 
as it combines with the oxyd of zinc constantly accumulating 
on the zinc plate, which must be removed as fast as formed, 
in order to keep up a steady flow of electricity. 

233. The theories which have been proposed to account 
for electro-chemical decomposition and the action of the 
voltaic circuit, we cannot discuss here, any further than to 
say that the chemical theory first proposed by Dr. Wollaston 
is now generally accepted. Volta argued that the contact 
of different metals was essential to the production of a cur- 
rent. The researches of Faraday, however, in cod firming 
the chemical view of Wollaston, have completely disproved 
the contact theory. A very simple experiment by Faraday 
illustrates this statement. A slip of amalgamated sheet 
zinc bent at a right angle is hung in a glass of dilute acid; 
on it is laid a folded piece of bibulous paper moistened with 

In other words, what do we say ? Conversely, what ? 232. How 
does a current pass in the cells of a battery ? What happens in each 
cell ? What is requisite in the fluid used to excite a battery ? How 
does acid water act in the battery? 233. What two theories have been 
proposed to account for the electrical phenomena of electrolysis ? What 
simple experiment disproves the contact theory ? 





iodid of potassum. A .platinum plate, with an 
attached wire of the same metal, is now placed in 
the acid water, but not in contact with the zinc; 
the sharpened end of the wire is bent, so as to 
touch the moistened paper, and very soon it is 
discolored by a brown spot made by the freo 
iodine, liberated from the electro-chemical de- 
composition of the iodid of potassium, with which 
the paper is moistened. There is no contact of 
metals, and the current is excited only from the 
Fig. 204, decomposition of the iodid out of the cell, and of 
the water in it. A very strong argument in favor of the 
chemical theory has been before mentioned, that the di- 
rection of the current is always determined by the nature 
of the chemical action — the metals most acted on being 
always positive. 

234. The electrotype, or deposition of metals from their 
solution by the voltaic current, seems to have been suggested 
by Daniell's battery. It has been remarked, that the cop- 
per of the sulphate of copper in the outer cell of that battery 
is deposited in a metallic state. The procuring of a pure 
metal in a perfectly malleable state, by means of a current 
of electricity, is a most important fact, and has given rise 
to a new and valuable art, which has become wonderfully 
extended in its applications. We thus accomplish, in fact, 
a cold casting of copper, silver, gold, zinc, and many other 
metals; and a new field of great extent has been thus 
opened for the application of metallurgic 
processes. The tinting of metals of various 
hues by metallic oxyds*, and the coloring of 
their surfaces by palladium, are among the 
most surprising of its effects. The very 
simple apparatus required to show these re- 
sults experimentally, is represented in the 
figure, (205.) It is nothing, in fact, but 
a single cell of Daniell's battery. A^lass 
tumbler S, a common lamp-chimney P, 
with a bladder-skin tied over the lower end 
and filled with dilute acid, is all the appara- 
lg * ' tus required. A strong solution of sulphate 
of copper is put in the tumbler, and a zinc rod Z in P, 

234. What is the electrotype? Explain its uses. 




the moulds, or casta, m m are seen suspended by wires 
attached to the binding screw of Z. Thus arranged, the 
copper solution is slowly decomposed, and the metal is 
evenly and firmly deposited on m, m. A perfect reverse 
copy of m is thus obtained in solid, malleable copper. The 
back of m is protected by varnish, to prevent the ad- 
hesion of the metallic copper to it. In this manner the 
most elaborate and costly medals are easily multiplied, and 
in the most accurate manner. In practice, casts are made 
in fusible metal of the object to be copied, and the operation 
is conducted in a separate cell, containing only the sulphate 
of copper, one of Smee's batteries supplying the power. 
The art is also now extensively applied to plating in gold 
and silver from their solutions ; the metals thus deposited 
adhering perfectly to the metallic surface on which they are 
deposited, provided these be quite clean and bright 

All the copper-plates of the charts of the Coast Survey are 
reproduced by the electrotype — the originals are never used 
in the press, but only the copies, and any required number 
of these may be produced at small expense. 





235. The number of elements, (or simple substances,) as 
now recognized, is sixty-two, forty-nine of which are metals 
The elements are usually divided into metals and metalloids, 
or non-metallic substances. This convenient distinction is 
not strictly accurate, since there are several elements, as 
tellurium, carbon, arsenic, silicium, and others, which seem 
to possess an intermediate character. The term metalloid 
is therefore preferable. Only fourteen of the elementary 
bodies are of common occurrence, and of these the atmo 
sphere, water, and the great bulk of the planet are com- 
posed. The remainder are comparatively rare, and are known 
only to the chemist. Of these, twenty-one, marked in the 
table with an asterisk (*), will not be discussed in this work, 
or will be very briefly considered, because of their great rarity, 
and the difficulty of procuring the substances containing 

236. At common temperatures, and when set free from 
combination, nearly all the elements are solids. Two, mer- 
cury and bromine, are fluids, and five are gases, namely, 
chlorine, fluorine, hydrogen, oxygen, and nitrogen. A few 
only of the elements are found naturally in a free or un- 
combined state, among which we may name oxygen, nitro- 
gen, carbon, sulphur, and nine or ten metals. All the rest 
exist in combination with each other, and so completely 
disguised as to manifest none of their properties. 

237. The names of the elements are arbitrary or conven- 
tional, while the nomenclature of their compounds is sub- 
ject to the strictest laws. Some of the elementary bodies 
have been known from the remotest antiquity, and were in 
common use long before the science of chemistry was heard 
of. Thus several metals, as Copper, (Cwprwm,) Gold, 
(Auruniy) Iron, (Ferrumf) Mercury, {Hydrargyrum^) Sil- 

235. What is the number of elements? How divided ? What occupy 
an intermediate position ? 236. What is the physical condition of th« 
elements ? Which are fluid ? Which gaseous ? Which found uncoin- 
bined ? 237. What of the names of elements ? Which have been long 
known ? 




ver, (Argentum,) Lead, (Plumbum,) Tin, (Stannum,) have 
long Deen known either oy the names we now give them, or 
by those Latin terms of which our English names are trans- 
lations. The alchemists named the metals after the various 
planets. Thus, Gold was called Sol, the Sun ; Silver, Luna, 
the Moon; Iron, Mars; Lead, Saturn; Tin, Jupiter; Quick- 
silver, Mercury ; and Copper, Venus. Hence, formerly the 
astronomical signs or symbols of these planets were employed 
(o represent the names of these metals, and they are still in 
use in some countries. 

Several of the elements have been named from some 
prominent or distinguishing physical property of color, taste, 
or smell, which they possess : thus, Bromine is so called 
from the Greek word bromos, fetor; Chlorine, from chloros, 
green, in allusion to its greenish color; Chromium, from 
chroma, color, because it makes highly-colored compounds, 
as chrome-yellow; Glucinum, from glukus, sweet, from the 
sweet taste of its salts ; Iodine, from ion, a violet, and eidos, 
in the likeness of. Another class of names has been con- 
trived from what was supposed to be the characteristic at- 
tribute of the body in combination. Thus, Oxygen was so 
named because many of its compounds are acids, from the 
Greek, oocus, acid, and gennao, I produce. Hydrogen is 
from hudor, water, and gennao, I produce. 

238. It has been discovered that the elements, in com- 
Dining among themselves, unite always in certain weights, in- 
variable in each case, and supposed to have an immediate re- 
lation to the atomic constitution of the substance. These 
weights represent respectively the quantities in which the 
elements unite with each other, and they are called equiva- 
lent atomic weights or combining numbers. In the follow- 
ing table, the equivalent or combining numbers of all the 
elementary bodies are given in accordance with the latest 
and best authorities. Because hydrogen enters into combi- 
nation with other bodies in a smaller weight than any other 
known element, it has generally been used in Great Britain 
and in this country as the basis of the scale of equivalent 
numbers. It is supposed also, by some good chemists, that 
the numbers expressing the combining weights of all bodies 

What of astronomical signs ? Whence such names as bromine, Hy- 
drogen ? Iodine, Ac. ? 238. How do the elements unite ? What do the 
weights represent ? What are they called ? Why is hydrogea unity ? 





would be found, on more accurate research, to be simple 
multiples of the unit of hydrogen. If this view were cor- 
rect, it would give us the great convenience of avoiding 
fractional numbers. The latest investigations have so far 
confirmed this idea, that in the present edition of this work 
a largely increased number of elements stand with simple 
numbers. Berzelius determined more atomic numbers than 
any other chemist, and his labors have in most cases stood 
the severest review, and deserve the everlasting gratitude of 
chemists. Most chemists of continental Europe assume 
oxygen as 100 ; therefore, to convert the numbers of the fol- 
lowing table to the oxygen scale, multiply them by 12*5. 




Antimony (Stibium) 



♦Beryllium (Glucinum) 

Bismuth , 









Cobalt , 

•Cnlumbium (Tantalum) 





Gold (Aurum) 






Lend (I'lumbum) 






137 t 
129- | 

75- I 




























































Potassium (Kalium) 



. Selenium 


I Silver (Argentum) 

I So;lium (Natrium) 

I Strontium 

i Sulphur 

I Tellurium 

i *Terbium 

i *Thorium 

Tin (Stannum) 









H =!• 



























































Combination by Weight. 

239. The laws by which the elements unite to form com- 
pounds, are included in the four following propositions : — 

What of its multiple relations ? Who determined most atomic weights t 




1st. The law of definite proportions, or, a compound of 
two or more elements, is always formed by the union of 
certain definite and unalterable proportions of its constituent 

2d. The law of multiple proportions, which requires that 
when two bodies unite in more proportions than one, these 
proportions bear some simple relation to each other. 

3d. The law of equivalent proportions, according to which 
when a body (A) unites with other bodies, (B, C, D, &c.,) 
the proportions in which B, C, and D unite with A shall 
represent in numbers the proportions in which they will 
unite among themselves, in case such union takes place. 

4th. The law of the combining numbers of compounds, 
by which the combining proportion of a compound body is 
the sum of the combining weights of its several elements. 

240. These general laws of combination are subject to 
some modifications, which will be explained as they arise. 
The first of the laws above given is the result of chemical 
analysis, and is proved by synthesis. Thus, from nine grains 
of water we obtain eight grains of oxygen and one of hydro- 
gen, and by the union of the like weights of these two sub- 
stances we obtain nine grains of water. Constancy of com- 
position is the essential feature of chemical compounds. 

By the law of multiple proportions we learn that if a body 
(A) unites with a body (B) in more proportions than one, 
these proportions bear a simple relation to each other. 
Thus, we may have the series of compounds A -f- B : A -f- 2B 
: A -}- 3B : A -f- 4B : A -f- 5B, as in the case of nitrogen 
and oxygen, between which this very series occurs, forming 
five distinct compounds, in which one, two, three, four, and 
five, parts by weight (atoms) of oxygen unite with one of 
nitrogen. (2.) In place of this simple ratio we may have 
one intermediate : thus, the expressions 2 A -(- 3B : 2A -j- 
5B : 2A+7B represent a series of compounds which 
are equal to the fractional ratios 1:1 J, 1:2}, 1 : 3 J. 

241. As by chemical analysis the law of definite proportions 
is established, so by the same direct experimental method do 
We prove the law of equivalent proportions. Oxygen is an 
element forming at least one definite compound with every 

239. What is the 1st law of combination? The 2d? The 3d? The 4th? 
240. Whence is law 1st derived ? Give an example ? What of the law of 
multiple proportions? Give examples of the 2d modification? 241. How is 
the law of equivalent proportions demonstrated ? What is said of oxygen ? 




other element known, except fluorine. These compounds are 
termed oxyds, (246.) By analysis we find that water always 
contains in 100 parts 11*11 parts of hydrogen and 88*89 parts 
of oxygen. If we ask how much oxygen is proportional, 
or equivalent to a unit of hydrogen, we state the simple 
proportion 11*11 : 100 : : 88*89 : x in which x = 8, which 
is therefore the equivalent of oxygen. In like manner, we 
might go on making analyses of all the compounds of oxygen 
until we had completed the whole list, when wo should have 
a table of equivalents for all the elements, hydrogen being 
unity. Thus, 

8 parts of oxygen unite with • 

10 parts of sulphur, 
6" parts of carbon, 
1 part of hydrogen, 

35*5 parts of -chlorine, 
100 parts of mercury, 

28 parts of iron, 

14 parts of nitrogen. 

Of course, 16, 6, 1, 35.5, 100, 28, and 14, are respec- 
tively the equivalents of sulphur, carbon, hydrogen, chlo- 
rine, mercury, iron, and nitrogen. Chemical equivalent and 
atomic weight have the same meaning in this work. 

242. If any of those bodies unite to form compounds, the 
union will always happen in quantities by weight exactly 
proportional to those numbers. Thus, hydrogen (1) unites 
with chlorine (35*5) to form chlorohydric or muriatic acid. 
In 36*5 pounds, therefore, of this acid, there will be 1 pound 
of hydrogen and 35*5 pounds of chlorine. If sulphur com- 
bines with mercury, it will require 16 parts of sulphur and 
100 parts of mercury, and there will be 116 parts of sul- 
phuret formed ; or it may require 32 parts of sulphur to 
100 parts of mercury, when we should have a bisulphuret. If 
oxygen is assumed as the standard of comparison for atomic 
weights, then, calling it 100, hydrogen will be 12*5, and all 
the other elements will have numbers just twelve and a half 
times as large as their equivalents on the hydrogen scale. 

It follows, as a necessary result of this law of equivalent 
proportions, that the combining numbers of a compound 
should be the sum of the equivalents of its constituents. 

Give the mode of determining atomic weights ? Give some examples ? 
What is the meaning of chemical equivalent? Of atomic weight? 
242. What is the relation among elements in combination? How is it 
in chlorohydric acid ? In sulphurct of mercury ? What of the combining 
numbers of compounds ? 




Chemical Nomenclature and Symbols. 

243. It would have been a hopeless task for the strongest 
memory to retain all the names of chemical compounds, if 
they had — like the names of the elements — been bestowed 
by the caprice of those who first discovered, or described 
them. A committee of the French Academy, with Lavoi- 
sier at their head, in 1787, settled the principles of chemi- 
cal nomenclature, which endure to this day, although the 
actual state of the science requires great changes in them. 
All chemical compounds are made to derive their names from 
one or more of their constituents. Before stating the rules 
of nomenclature, we must define certain general terms of 
common occurrence. 

244. Bodies are divided into acids, bases, and salts. Salts 
result from the union of acids with bases. By the voltaic pile 
salts are decomposed (228 [6]) into acids and bases — the 
acids go to the positive pole, the bases to the negative. We 
therefore call the acid, in reference to electrical law, the 
electro-negative constituent, and the base the electro-positive. 
This is equally true of those compounds which render up 
their elements in electrolysis as of salts which are simply 
separated into acids and bases : e. g. common salt by elec- 
trolysis yields chlorine, an electro-negative element, and 
sodium, an electro-positive one. The former is an acid, the 
latter a base. 

Acids and bases are further distinguished, in that acids 
redden the blue vegetable infusions, while bases restore the 
colors which the acids have reddened. Some vegetable 
colors, like syrup of violets, or tincture of dahlia or of pur- 
ple cabbage, are made green by alkalies, and are reddened 
by acids. If no change of this sort is indicated, the body is 
said to be neutral. 

245. When two elements unite, the product is called a 
binary compound, from bis, twice; thus water, sulphuric 
acid, oxyd of silver, and oxyd of iron, are binary compounds. 
Compounds of binary combinations with each other, as of 

243. What of the names of compounds ? Who settled the principles 
of nomenclature ? How are the names divided ? 244. How are bodies 
divided? How are salts formed ? What of the pile ? What does electro- 
positive mean ? What electro-negative ? How of common salt ? How 
are acids and bases further distinguished? What is neutrality ? 245. 
What is a binary compound ? 

Digitized^ VjOOQ IC 


sulphuric acid with soda, forming sulphate of soda, or Glau- 
ber's salts, are called ternary compounds, (from ter, thrice.) 
Compounds of salts with each other, (as in the case of alum, 
which is a compound of sulphate of potash and sulphate of 
alumina,) are named quaternary compounds, from quatuor, 

246. The compounds of oxygen are called either oxyd$ 
or acids : thus, water is an oxyd of hydrogen ; and one of the 
oxygen compounds of sulphur is called sulphuric acid. 
The binary compounds of chlorine, bromine, iodine, fluo- 
rine, and some other elements, which resemble oxygen in 
their mode of combination, are also distinguished by the 
same termination id or ide. Thus, chlorine forms chlorids; 
bromine, bromids ; iodine, iodids ; and fluorine, fluorids. 

The binary compounds of sulphur, selenium, phosphorus, 
arsenic, and some others, receive usually the termination uret. 
Thus we say sulphuret, seleniuret, phosphuret, &c., although 
sulphid, selenid, phosphid, &c, are more in obedience to 
the rules of the nomenclature. 

247. In all cases, the name of the electro-negative con- 
stituent of a compound rules the name of the genus of the 
compound. Thus, chlorid of potassium, sulphuret of iron, 
and sulphate of soda, all imply that the chlorine, sulphur, or 
sulphuric acid, are the electro-negative constituents, and 
that potassium, iron, and soda are the electro-positive ele- 
ments in those compounds. The same rule holds in all the 
salts also, however complex. 

248. When the same element unites with oxygen in more 
than one proportion, forming two or. more oxyds, then 
these are distinguished as protoxyd, deutoxyd, tritoxyd, from 
the Greek protos, first ) deuteros, second ; and tritos, third ; 
corresponding to the first, second, and third degree of oxyda- 
tion. The word hi (double) binoxyd is also used in place of 
deutoxyd. The oxyd which contains the largest proportion 
of oxygen with which the body is known to unite, is also called 
the peroxyd, from the Latin, per, which is a particle of in- 
tensity in that language. Thus, there are two oxyds of 
hydrogen, the protoxyd (water) and the peroxyd. There 

A ternary ? A quaternary ? 246. What of the oxygen compounds ? 
How of the compounds of chlorine, Ac. ? How of sulphur, Ac. ? 247. 
What of the electro-negative constituent? Give examples. 248. How 
are the first, second, third, Ac, oxyds distinguished? What are hi- 
noxyds ? 




are three oxyds of manganese: 1. The protoxyd; 2. The 
deutoxyd; 3. The peroxyd of manganese. Some oxyds are 
formed in the proportion of 2 to 8, or once and a half. 
Such oxyds are distinguished by the term sesquioxyds, from 
the numeral sesqui, (once and a half.) Certain inferior 
oxyds are called suboxyds, as suboxyd of copper, Cu 9 0. 

249. The acid compounds of oxygen derive their names 
by adding the terminations ous or ic with the word acid to 
the electro-negative constituent. Thus, for the two acids of 
sulphur we have sulphurous acid and sulphuric acid : the 
first signifies the lowest, the second the highest oxygen 
compounds of the substance known at the time when the 
rules of the nomenclature were framed. As the progress of 
science has made known other and intermediate compounds, 
in order to bring them into the system, it was necessary to 
employ the terms hypo and hyper, from hupo, under } and 
huper, above. Thus, we have hyposulphurous and hyper- 
sulphurous, for two acids of sulphur respectively under and 
above sulphurous in their quantities of oxygen. The pre- 
fix per has been added to signify a degree of oxydation 
higher than that implied by ic. Thus, chloric acid was for 
a long time the highest known degree of oxydation of 
chlorine ) but now we have perchloric acid also. Peroxyd 
mean 8 the highest oxyd known. 

250. Sulphur, selenium, tellurium, arsenic, &c., and chlo- 
rine, bromine, iodine, and fluorine, also form acid compounds 
with hydrogen. These are named after the electro-negative 
compounds, sulphydric, selenhydric, chlorohydric, bromohy- 
dric, &c. Sulphuretted hydrogen, arseniuretted hydrogen, 
ftc, are also used, as well as hydrochloric, hydrobromic, 
&c. ; but the first named are more in accordance with the 
principles of the nomenclature. 

251. The salts (ternary compounds) are named in an 
equally simple manner. The acid supplies the generic, the 
base the specific name. Sulphate of soda, nitrate of potassa, 
sulphite of soda, and nitrite of potassa, are respectively salts 
of sulphuric, nitric, sulphurous, and nitrous acids. Thus, 

What sesquioxyds ? Suboxyds ? 249. How are the aeid compound! 
of oxygen named ? What of hypo and hyper ? What of the prefix per J 
Give examples. 250. How are acid compounds of sulphur, Ac, with 
hydrogen named? 251. How are salts named? What gives generic, 
and what ipecifio names ? How do the acids change the termination! 
out and ic ? 




in forming salts, the acids change the terminations ous and 
ic f into ite and ate. 

When there are more oxyds of a base than one entering 
into combination, the resulting salts are distinguished, for 
example, as sulphate of the protoxyd of iron or sulphate of 
the peroxyd. 

252. Chemistry enjoys the peculiar advantages of possess* 
ing a descriptive and defining nomenclature. Permanganate 
of potassa is not a trivial name, but supposing that we now 
saw it for the first time, we learn from its simple inspection 
that the compound contains permanganic acid, and the base 
potash ; and further, that the acid in question is the highest 
oxygen compound of manganese known. 

Convenient as the nomenclature of chemistry is, the pro- 
gress of the science has made known so many and such 
complex compounds, that it long since became necessary to 
devise some simple mode of notation by which they might 
be expressed, briefly and with certainty. Berzelius sup- 
plied this requisite in the system of chemical symbols, by 
which all chemical compounds may be described with mathe- 
matical precision. 

253. In the table of elementary bodies, (238,) the 
" symbols" of the several elements will be found opposite 
to their names. The symbols are merely the first letter of 
each name, or the first two. By a happy thought, Berzelius 
made each symbol represent not merely the substance for 
which it stands, but one equivalent of each substance. Thus, 
stands not for oxygen in general, but for one equivalent 
of that element; or, hydrogen being unity, for the number 
8. and 8 are therefore interchangeable expressions, whfl* 
O, O 8 , &c. represent 2 X 8 and 3 X 8, or 16 and 24. 

Compounds are represented by using merely the symbols, 
and sometimes uniting them by the sign of addition, (-f .) 
Thus, water will be represented by HO, or one equivalent 
of each element, 1 -f- 8 = 9, the combining number for 
water. Protoxyd of lead is thus written PbO ; and PbO 2 is 
the peroxyd. 

The co-efficient attached to a symbol signifies how many 

When there are more oxyds than one, how is it ? Give examples. 

252. What advantage of nomenclature has chemistry? Give an ex- 
ample. What inconvenience was found? Who supplied the want? 

253. What are symbols ? What do they express ? Give an instance 
What of co-efficients ? 



— .... 




atoms of tiie element are concerned : thus, 0, O 9 , 0*, 0*, ()•, x 

&G. y are respectively 1, 2, 3, 4, and 5 atoms of oxygen, which 
may also be written 0& 8 , &c, or 20, 30, 40, Ac. For- 
mulse are expressions by which we recognize the constitution 
of compounds; thus, sulphuric acid has the formula SO,, oxvd 
of iron is FeO, and sulphate of protoxyd of iron is FeO+SOg, 
oi one equivalent of that compound. Two equivalents 
would be written 2(FeO+S0 8 ). If we write 2FeO+SO„ 
it means two atoms of protoxyd of iron, plus one of sul- 
phuric acid. In chemical formulae, the electro-negative 
element is placed last, the electro-positive is written first 
Thus HO is water, not OH. When the sign plus is used 
in a chemical expression, it usually signifies a union less 
close than if a comma or no sign at all had been used. 
Thus SO, HO + 2H0 signifies a hydrate of sulphuric acid 
in which two atoms of water are loosely retained, while one 
is in more close combination. 

Water unites with bases 6> form hydrates, as the common 
hydrate of potash or hydrate of lime, and also with acids 
to form compounds analogous to salts. Thus, with sulphu- 
ric acid, forming what in strictness should be called a sul- 
phate of water ; but such cases are usually known as hydrated 
acids. As 1, 2, or 3 atoms of water may unite with an acid, 
so we have monohydrated, bihydrated, and terhydrated sul- 
phuric or phosphoric acids. 

254. Since chemical analysis only makes known to us 
the number of constituents found in a compound, and the 
mode in which these are arranged is undetermined, except 
by theoretical considerations, it is becoming more the habit 
0f chemists to write formulae expressing only the results of 
analysis. Thus, acetic acid is written C 4 H 4 0^ since this 
is the result of an analysis of this substance. In accord- 
ance with some views it is written C 4 H 8 8 +H0. Sul- 
phuric acid, usually written S0 8 HO, is written, perhaps 
more unexceptionably, S0 4 H. These two modes of expres- 
sion are denominated rational and empirical formulae. 

255. Professor Graham suggests what he calls antithetic 
or polar formulae, which shall place all the electro-positive 
elements of a compound in one line, and all the electro- 

What are formulae ? Give an example. Which constituent is placed 
first? What of sign-)-? Give an example. What of hydrates and 
acids ? 254. What two modes of stating analytic results are here men* 
tioned ? 255. What are antithetic or polar formulae ? 




negative in a line above them, like the numerators and de- 
nominators of fractions. Thus, water will be ~, sulphuric 

.,0. , Li . , 00, 4 
acid f, sulphate of soda m ff « or ^. 

256. The symbols are sometimes abbreviated still farther, 
to simplify the expression of very complex combinations. 
This is done by expressing one equivalent of oxygen by a 

dot, two, by two dots, &c. Thus, S signifies the same as S0 8 , 
(dry sulphuric acid.) Common crystallized alum is written 
in full, thus, 

Al s 8 >3S0 8 +KO,S0 8 +24HO. 

We can conveniently condense this long expression ; thus 
Al S 8 +KS+24H. 

The short line under the Al signifies two equivalents of the 
base. Sulphur is in like manner signified by a comma; 
thus, bisulphuret of iron, Fe,S 9 , may be more shortly 

written Fe. Symbolic formulae have contributed very much 
to the progress of the science, and are invaluable as a ready 
means of comparing as well as expressing the composition 
of compound bodies. 

257. There is an interesting relation between the atomic 
weights, the specific gravities, and the combining measures 
or volumes of those elements which exist in the gaseous 
state, or are capable of assuming it. One grain of hydro- 
gen occupies 46*7 cubic inches, but the same bulk or volume 
of chlorine weighs 35*5 grains, of nitrogen 14 grains, df 
iodine 127*1 grains, of bromine 80 grains, and of oxygen 
16 grains. These weights respectively represent the density 
of the several gases compared with hydrogen as unity ; but 
they are also identical with the atomic weights of the seve- 
ral elements, except oxygen, which is double. We have 
before seen (224) that two volumes of hydrogen and one 
volume of oxygen are evolved in the electrolysis of water. 
The volumes in which gaseous elements unite are therefore 
as 1 : 1 or as 1 : 2, or some simple ratio. Sulphur has J 
the volume of oxygen and mercury four times. The combin- 

256. How are symbols abbreviated ? Illustrate by alum. 257. What 
rotation is named between bodies in tbe gaseous state ? Give illustra- 
tions of this. How do elements unite by volume ? 





«og measure of oxygen being one volume, the combining 
folume of hydrogen, nitrogen, chlorine, bromine, iodine, 
and mercury, will be two volumes. 

258. In the following table, hydrogen is taken as the 
unit of combining measures, and we observe that where 
the numbers in the second column are the same as the 
equivalents, then a volume represents an equivalent; other- 
wise some simple multiple of it. As with sulphur (16X6 
=96) and oxygen, (2 X8=16.) 

Gases and Vapors. 

Specific Gravities. 

Chemical Equivalents. 



By volume. 

By weight 









100 or 1 
100 or 1 

50 or* 
100 or 1 
100 or 1 
100 or 1 
200 or 2 










Iodine vapor 

Bromine vapor 

Mercury vapor..... 
Sulphur vapor..... 

259. The combining measure of compound gases is vari- 
able, but they bear a simple and constant ratio to each 
other ; and hence the density of a compound gas may often 
be more accurately calculated from the known density of 
its constituents, and its change of volume in combination, 
than it can by direct experiment. A single example will 
illustrate this. Water consists of 1 atom of each of its 
constituents, represented by 1 volume of O and 2 vo- 
lumes of H. These three volumes weigh 1105-6+69 -3 
-|- 69 -3=1244 -2= two volumes of steam, one of which = 
half this sum, or 622, the density of steam, air being unity. 
From a comparison of the experimental results obtained by 
chemists, it appears that there exists a very simple relation 
between the combining measures of bodies in the gaseous 
state, compound as well as simple. Of a few bodies the 
combining measure is like that of oxygen, one volume ; of 
& large number double that of oxygen, or two volumes; 
of a still larger number four times that of oxygen, or four 
volumes ; while combining measures of three and vix, or of 
fractional portions of a volume, as one-third, are compara- 

258. Illustrate this further from the table. 259. How in compound 
gates ? What is the case with water? What relations are established ? 





lively rare. These results in regard to combining measures 
were first obtained by Humboldt and Gay-Lussac, and have 
afforded the most remarkable confirmation of the atomic 
theory of Dalton. 

260. Atomic volumes are those numbers which are ob- 
tained by dividing the atomic weights of bodies by their 
densities, and this whether we speak of simple or compound 
bodies. In mineralogy, as shown by Dana, this relation is 
often of great importance in determining the relations of 

Specific Heat of Atoms. 

261. Specific heat has already been explained, (117.) 
If in place of comparing equal weights of different bodies 
together, we take them in atomic proportions, we shall find 
the numbers representing the specific heat of lead, tin, zinc, 
copper, nickel, iron, platinum, sulphur, and mercury, to be 
identical ; while tellurium, arsenic, silver, and gold, although 
equal to each other, will be twice that of the nine previous 
bodies, and iodine and phosphorus will be four times as 
much. The general conclusion drawn from these and other 
similar facts is, that the atoms of all simple substances have 
the same capacity for heat. The specific heat of a body 
would thus afford the means of fixing its atomic weight. 
There can be no doubt of the truth of this in numerous 
cases, but experiments are still wanting to show it to be 
universally true. Compound atoms have in some cases been 
shown to have the same relations to heat as the simple. 
This is true of many of the carbonates, and some sulphates. 

Isomorphism and Dimorphism. 

262. Isomorphism is identity of crystalline form, with 
a difference of chemical constitution. Identity of crystal- 
line form was formerly supposed to indicate an identity of 
chemical composition. We now know that certain sub- 
stances may replace each other in the constitution of com- 
pounds, without changing their crystalline form. This 
property is called isomorphism, and those basis which admit 
of mutual substitution are termed isomorphous. Chemistry 

Who first observed these relations ? 260. What are atomic volumes? 
261. What of specific heat of atoms ? 262. What is isomorphism ? 
Give examples. 




furnishes us many examples of these isomorphous bodies. 
Thus, alumina and peroxyd of iron replace each other in* 
definitely. The carbonate of iron and carbonates of lime, 
magnesia, and manganese, are also examples, as the common 
sparry iron, (spathic iron,') which is a carbonate of iron, in 
which a large portion of carbonate of lime sometimes exists 
without producing any change of form in the mineral. Oxyd 
of zinc and of magnesia, oxyd of copper, and protoxyd of 
tron, also take the place each of the other in compounds, 
without any alteration of crystalline form. When those 
bodies unite with acids to form salts, the resulting com- 
pounds have the same crystalline form, and, if they have the 
same color, are not to be distinguished from each other by 
the eye. 

In double salts, like common alum, these relations are 
also found. Sulphate of iron may take the place of sul- 
phate of alumina in common alum, and no change of form 
will occur ; and soda may, in like manner, replace the pot- 
ash. In fact, all the similar compounds of isomorphous 
bodies have a great resemblance to each other in general 
appearance and chemical properties. The two bases in a 
double salt are, however, never taken from the same group 
of isomorphous bodies. 

263. A knowledge of this law is of great importance to 
the chemist,, and often enables him to explain, in a satis- 
factory manner, apparent contradictions and anomalies, and 
to decide many doubtful points. It is supposed that the 
elements whose compounds are isomorphous, are themselves 

The following group of isomorphous bodies is given by 
Professor Graham in his " Elements." 1st family : Chlo- 
rine, Iodine, Bromine, Fluorine. 2d family : Sulphur, 
Selenium, Tellurium. 3d family: Phosphorus, Arsenic, 
Antimony. 4th family : Barium, Strontium, Lead. 5th 
family : Silver, Sodium, Potassium, Ammonium. 6th fami- 
ly: Magnesium, Manganese, Iron, Cobalt, Nickel, Zinc, 
Copper, Cadmium, Aluminum, Chromium, Calcium, Hy- 

264. Dimorphism and Polymorphism. — Some substances 
have two forms, under both of which they are found. Thus, 

In what doable salts is it found ? 263. What does this law explain 1 
What groups are given ? 264. What are dimorphism and polymorphism 1 




common calc-spar (carbonate of lime) generally occurs io 
rhombohedrons, (49, fig. 13,) but in arragonite (which is onlj 
pure carbonate of lime) it is seen as a rhombic prismj 
(46, fig. 37.) 

Bin-iodid of mercury is another example of the same 
kind; and in both these cases the change of form is effected 
by heat Polymorphism is where more than two forms of 
the same substance are known; as in titanic acid, of which 
rutile, anatase, andbrookite are three distinct orystallographio 

Chemical Affinity. 

265. Chemical affinity, or the capability of chemical 
union between bodies, is not possessed alike by all. Oyxgen 
is the only element capable of forming chemical compounds 
with all other elements. Carbon can unite with oxygen, 
sulphur, hydrogen, and some other bodies, but no coin* 
pound has been formed between it and gold, silver, fluorine, 
aluminum, iodine, and bromine. It is, therefore, said to 
have no affinity for those bodies, or no capability of union 
with them. The power of union among bodies, or affinity, 
is exceedingly different in degree, and is much affected by 
many circumstances. Thus A may unite with B, forming 
AB ; but if C had been present, A might have so much 
more affinity for C than it has for B, as to unite with it, 
forming AC, while B would remain unaffected. For exr 
ample, sulphuric acid and soda unite to form Glauber's salts, 
or sulphate of soda; but if soda and baryta had both been 
present, and sulphuric acid were added, only the sulphate 
gf baryta would be formed, and the soda would remain dis- 
engaged, unless there was sulphuric acid enough to satisfy 
both. This is what is sometimes called elective affinity, as 
if the acid selected the baryta rather than the soda. 

266. The more unlike, as a general thing, any two bodies 
are in chemical properties, the stronger is their disposition 
to unite. The metals, as a class, have very little disposition 
to unite with each other. But they unite with oxygen, 
chlorine, and sulphur, forming fixed and determinate com- 
pounds. The alkalies, potash and soda, form no proper 

265. What of chemical affinity ? What of oxygen ? What of carbon ? 
What determines the union of A and B? How if C were present? 
What is this sort of affinity called ? 266. What of the similarity of 
bodies ? Illustrate by an example. 




compound with each other, and their alkaline properties are 
not altered hy such union. Sulphuric and nitric acid may 
be mingled in any proportion, but no new compound is 
formed, and the mixture is still acid. But if the potash 
%nd soda respectively be added to nitric and sulphuric acid, 
the result will be saltpetre, or nitrate of potash, and Glau- 
ber's salts, or sulphate of soda, two salts having neither 
alkaline nor acid properties. 

267. Solution is the result of a feeble affinity, but one in 
which the properties of the dissolved body are unaltered : 
thus, sugar is dissolved in all proportions in water or weak 
alcohol. Camphor is soluble in alcohol, but the addition 
of water to the solution will, by engaging the alcohol, cause 
the camphor to be thrown down. Gum is soluble in water, 
but not in alcohol. We have already seen that the solu-, 
tion of various salts in water would produce cold (124) from 
the change of state in the body dissolved; 

268. The circumstances which modify the action of 
affinity are numerous, some of which we may briefly notice. 
We have said (8) that chemical affinity existed only among 
unlike particles, and at insensible distances. Intimate con- 
tact among particles is, therefore, in the highest degree 
necessary to promote chemical union. Any circumstance 
which favors such contact will increase the activity of, or 
disposition to, chemical combination. Solution brings par- 
ticles near together, and leaves them free to move among 
each other: substances in a state of solution have, there- 
fore, an opportunity to unite, which they do not possess 
when solid. Hence the old maxim, " Corpora non agunt 
nisi sint soluta." Carbonate of soda and tartaric acid, foe 
example, both in a dry state, remain unchanged; but the 
addition of water will at once, by dissolving them, bring 
about a union. Heat being, in fact, a most powerful means; 
of solution; will often eause union to take place. Sand or: 
silica will not unite with soda or potash by contact or aque- 
ous solution, but if the mixture in proper proportions is. 
strongly heated, union takes place and glass is formed. 
Sulphur will not unite with cold iron, but if the iron be, 
heated to rednesss, or the sulphur melted, a vigorous union 
takes place, and a sulphuret of iron results. Cohesion is 
destroyed by heat and solution, and substances in fine 

267.. What of solution? 208. Name circumstances affecting affinity. 

Digitized by VjOOQIC 


powder unite more readily than in masses of large sise. 
Dry sal-ammoniac and dry lime, in fine powder, mingled 
together, evolve ammonia. This is an interesting example 
of chemical action, by mere contact of dry substances. 

269. Bodies in the nascent state (as it is called) will 
often unite, when under ordinary circumstances no affinity 
is seen between them. Thus hydrogen and nitrogen gases, 
under ordinary circumstances, do not unite if mingled in tho 
same vessel ; but when these two gases are set free at the 
same timej from the decomposition of some organic matter, 
they readily unite, forming ammonia. The same is true of 
carbon under the same circumstances, which will then unite 
in a great variety of proportions with hydrogen and nitrogen, 
although no such union can be effected among these bodies 
under ordinary circumstances. 

270. The quantity of matter, as well as the order and 
condition in which substances may be presented to each 
other, often exerts an important influence on the power of 
affinity. Thus, vapor of water, when passed through a gun- 
barrel heated to redness, will be decomposed, the oxygen 
uniting with the iron, while the hydrogen escapes at the 
other end of the tube. On the contrary, if dry hydrogen is 
passed over oxyd of iron in a tube heated to redness, the 
hydrogen unites with the oxygen of the oxyd of iron, leav- 
ing metallic iron, while vapor of water escapes at the open 
end of the tube. Other examples of this sort are observed, 
where the play of affinities seems to be determined by the 
preponderance of one sort of matter over another, or by the 
peculiar condition of the resulting compounds, as regard* 
insolubility, or the power of vaporization. 

271. The presence of a third body often causes a union, 
or the exertion of the force of affinity, when this third body 
takes no part in the changes which happen. Thus, oxygen 
and hydrogen gases may be mingled without any combina- 
tion taking place between them, although a strong affinity 
exists. If, however, a portion of platinum in a state of 
very fine division (spongy platinum) be introduced into the 
mixture, union takes place, sometimes slowly, but more 

269. What of the nascent state ? Give an example. 270. What ol 
quantity of matter ? What is catalysis ? Give examples. 

• From nascent, being born, or in the moment of formation. 

Digitized by VjOOQ IC 


often with an explosion, the platinum being at the same 
time heated to redness from the rapid condensation of the 
gases which takes place in its pores. Advantage is taken 
of this fact in constructing the common instrument for 
lighting tapers by a stream of hydrogen falling on spongy 
platinum. No change is suffered in this case by the plati- 
num, which seems to act by its presence only. Berzelius 
has proposed the term catalysis, from the Greek kata, by, 
and luo 9 to loosen, to express the peculiar power which 
some bodies possess of aiding chemical changes by their 
presence merely. 





272. It is usual to divide elementary bodies into two great 
groups, the non-metallic and metallic elements. This con- 
venient arrangement is founded on characters which in a 
general and popular sense are correct and easily distinguished, 
but which fail in several cases to afford any accurate distinc- 
tion. No one can doubt to which class, for example, gold 
and sulphur should be respectively referred; but it is im- 
possible to say why carbon and silicon are not as well entitled 
to be classed in the same group with the metals as tellurium 
and arsenic, if we except the single character of lustre. 

We will discuss the first division of elementary bodies in 
six classes, in the following order : — 

}The only element which forms compounds 
with all others, and the type of electro-ne- 
gative bodies. 
Four elements very similar in all their 
. sensible properties, forming similar com- 
. pounds with the metals, whose acid com- 
. pounds with oxygen are also similar, and 
. have the constitution expressed by RO, 
J R0 4 , RO„ ROt. 

These stand in close relation with each 
other, while their compounds with the me- 
' tals are more similar to the oxyds of those 
' metals than are the analogous compounds 
of the second class. Their oxygen acids 
have the formula RO* RO* 

This group properly includes also arsenio 
and antimony, which are, however, from 

9. Nitrogen convenience, discussed elsewhere. The 

10. Phosphorus . ' four form similar compounds with oxygen, 
RO, RO t ,' ROi, and peculiar gaseous com- 
pounds with hydrogen, RH» 

Class ii. 

Class hi. 

Class IV. 

2. Chlorine.. 

3. Bromine.. 

4. Iodine.... 

5. Fluorine.. 

6. Sulphur... 

7. Selenium. 
S. Tellurium... 

Class v. 

Class vl 

J 11 C bo 1 These three bodies are similar, non-vola- 

19 (y\ ' I tile, combustible bases, and alike in form- 
iz. biucon fing feeble acids with, oxygen. The formula 

I "' 15oron J. RO, is adopted by some chemists. 

This highly electro-positive body is un- 
like any of the preceding, and has analogies 
with the succeeding group of metals. 

•j 14. Hydrogen. > 

272. How are the elements divided ? What of the accuracy of this 
division ? How many classes are named for 1st division ? Name the 
1st class, the 2d, the 3d, the 4th. What other elements belong to this 
group ? What is the formula of the hydrogen compounds of this group t 
What is class 5 ? Class 6 ? 



oxroEN. 1611 

273 We will consider these several classes separately. 
The compounds which each element forms with those before 
it, will be taken up in order ; and we shall then be better 
able to understand the relation of each element to its asso- 
ciates in the same group. The several classes, too, will then 
be better understood in the analogies which unite, and the 
differences which separate them. 



Equivalent , 8. Symbol, 0. Density, 1*106. 

274. Dr. Priestley discovered oxygen in 1774. It was 
also rediscovered by Scheele, of Sweden, immediately after, 
and without a knowledge Of Priestley's discovery. Before 
this time, all gaseous bodies were considered to be only modes 
of common air, and oxygen was first called vital air, and, 
in allusion to the then existing theories, depMogisticated 
air. It was the illustrious Lavoisier, author of the present 
nomenclature of chemistry, who proposed the name oxygen, 
(from oxus, acid, and gennao, I form.) Lavoisier had also 
rediscovered oxygen in 1775. At that time it was supposed 
that all acids contained oxygen. 

Oxygen is the most widely diffused and important of the 
elements. It forms over one-fifth part of the atmosphere 
by weight, eight-ninths of the waters of the globe, and pro- 
bably one-third part of its solid crust. It has also the widest 
range of affinities of all known substances, and by its im- 
mediate agency combustion and life are alone sustained. 

275. Preparation. — Oxygen gas is procured by heating 
the oxyds of lead, mercury, or of manganese, or the salts, 
nitrate of potassa, chlorate of potassa, or nitrate of soda. 
Chlorate of potassa is, however, the salt generally em- 
ployed, as yielding a large volume of pure oxygen with a 
gentle heat. This salt contains six equivalents of oxygen, 
and parts with them all at a moderate heat, leaving a residue 
of chlorid of potassium. Thusei0 5 KO==ClK + 60. One 
ounce of chlorate of potassa yields 543 cubio inches of pure 
oxygen, or over a gallon and a half. The arrangement of 

273. In what order are they discussed ? 274. Who discovered oxygen, 
and when ? How were gases formerly considered ? Who named oxygen ? 
Whence the name? What of the importance and dufusion of oxygen? 
276. How is it prepared? 





apparatus for this purpose is shown in fig. 206. A con* 
veuient portion of chlorate of potassa is pulverized and mixed 

with its own weight of 
manganese, or better 
with the black oxyd 
of copper. The dry 
mixture is placed in 
the flask a of hard 
glass, where it is 
heated by the lamp 
below. A bent tube 
fitted to a by a cork, 
conveys the gas to the 
air-bell b, previously 
Fig. 206. filled with water and 

inverted in the water-trough. The heat of the lamp decom- 
poses the salt, and pure oxygen is freely given off, displacing 
the water in the air-jar. By aid of the oxyds of manganese 
or copper the decomposition of the chlorate of potassa is 
rendered gradual and safe. Without this precaution the 
operation proceeds with almost ungovernable energy; the 
whole volume of gas being given off almost at the same instant, 
when the point of decomposition is reached. The metallic 
oxyd seems to act by distributing the heat, and by the me- 
chanical distribution of the salt: clean sand may be used 
with nearly equal success. The glass may be protected from 
fusion by a thin metallic cup c employed as a sand-bath. 

276. When large 
volumes of oxygen 
gas are required, a 
more economical 
plan is to heat the 
peroxyd of man- 
ganese strongly in 
an iron retort ar- 
ranged in a rever- 
beratory furnace, 
(fig. 207.) One 
pound of good oxyd 
Fig. 207. of manganese will 

Give the way by chlorate of potassium. Why is oxyd of manganese 
used ? How does it act ? 276. What is the process by fig. 207 ? 






yield seven gallons of oxygen, with some carbonic acid. Thii 
last is removed by passing the gas through t^e wash-bottlo 
w containing solution of potash, which absorbe carbonic acid. 
In this process Mn0 9 becomes MnO + 0; about twelve 
per cent, of the weight of oxyd employed being obtained 
as oxygen. Oxygen gas may also be procured from oxyd 
of manganese by aid of strong sulphuric acid and a moderate 
heat. The mixture is placed in a balloon d, (fig. 208,) and 
heat applied. 
Sulphate of 
manganese is 
formed, and 
half the quan- 
tity of oxygen 
in the original 
oxyd, or one 
equivalent, is __ y 
given off. Car- "" 
Sonic acid is 
removed by 
thepotoshso- B * So- 

lution in w. Bichromate of potash may be substituted for 
the oxyd of manganese in this case with good results. Both 
should be in fine powder. 

277. Properties and Experiments. — Oxygen, when pure, 
is a transparent, colorless gas, which no degree of cold or 
pressure has ever reduced to a liquid state. It is a q 
little heavier than the atmosphere, its density being, 
compared to air, as 1-1057 : 1 -000. One hundred cubic 
inches of the dry gas weigh 34*19 grains. It is without 
taste or smell. It is very slightly dissolved in water, 
one hundred volumes of water dissolving only about 
four and a half of the gas. Its most remarkable pro- 
perty is the energy with which it supports combustion. 
Any body which will burn in common air, burns with 
greatly increased splendor in oxygen gas. A newly 
extinguished candle or taper, (fig. 209, J which has the 
least fire on the wick, will instantly be rekindled in 
oxygen, and burn in it with great beauty. A quart FigTaw, 

How is gas of this source purified ? What is the reaction of heat 
on manganese ? How is O procured by sulphuric acid as in fig. 208 ? 
277. What are the properties of O ? How does it act oq combustibles? 





bifr 210, 

of this gas in a narrow-mouthed bottle, will 
easily relight a candle fifty times. A bit of 
charcoal bark (fig. 210) with only a spark of 
ignition on it, attached to a wire and lowered 
into a jar of this gas, will burn with intense 
brilliancy, producing carbonic acid. A steel 
watch-spring dipped in melted sulphur and ig- 
nited, when lowered into a jar of pure oxygen 
.ltm, bursts into the most magnificent combus- 
tion, (fig. 211.) The oxyd of iron 
which is formed falls down in burn- 
ing globules, like glowing meteors, 
which fuse themselves into the glazed 
surface of an earthen plate, although 
covered with an inch of water. If, 
as often happens, a motion of the 
spring throws a globule of this fused 
oxyd against the side of the glass 
vessel, it melts itself into the sub* 
stance of the glass, or, if that is thin, 
goes through it. This is one of the 
most brilliant and instructive expe- 
Fig. 211. riments in chemistry. If the ori-» 

fice at top is closed air-tight, and water is poured into the 
plate, we shall find, as the experiment, proceeds, that the 
water will rise in the jar as the gas is consumed. If we 
could collect and weigh the globules of oxyd of iron, we 
should find in them an increase of weight equal to the 
weight of the oxygen consumed. 

If the watch-spring or wire is coiled 
into a helix, as in fig. 212, then the com- 
bustion proceeds in a most beautiful 
series of revolutions, greatly heightening, 
the splendor of the experiment. These 
experiments should be conducted in a. 
dark room to have the full effect of their 

If the flame of a lamp, (Fig. 213,) is 
supplied by a jet of oxygen, the tempe- 
rature of combustion is so much elevated 

Fig. 212. 

Explain the experiments in figs. 210, 211, and 212. 



OXYGEN. 173 

that a £latina wire may be fused in it* We 
thus imitate the oxyhydrogen blow-pipe to 
be described further on, (885,) 

278. Oxygen, when inhaled, affects life by 
quickening the circulation of the blood, and 
causing an excitement, which, if continued, 
would result in general inflammatory symp- " Fie. 213. 
toms and death. In an atmosphere of pure 
oxygen we would live too fast, exactly as combustion is 
too rapid in an atmosphere of this gas. It exerts, how- 
ever, no specific poisonous- influence, being, when used in 
moderation, altogether salutary, and often resorted to, to 
inflate the lungs of drowned persons, and not unfrequently 
with the most beneficial results. The blood is constantly 
brought into contact with the air in the lungs, and it is 
the oxygen in the air which is the active agent in render- 
ing it fit to sustain life. Pure oxygen is constantly supplied 
to the atmosphere by the processes of vegetable life. 

279. Ozone, the allotropic or double condition of oxygen. 
When a stream of electrical sparks is passed through a tube 
in which a current of dry pure oxygen is flowing, the gas 
assumes new properties. The same result is obtained also 
where water is electrolysed, (224,) when phosphorus slowly 
consumes in a globe of moist air, or when a Leydeh battery 
is discharged. In all these cases there is a peculiar odor, 
perceived also after a powerful discharge of electricity from 
the clouds. Hence the name ozone, from ozumi, to smell. 
However this result may be obtained, it is observed that 
oxygen in this condition, or air containing it, presents much 
more powerful oxydizing powers than ordinary oxygen. It 
will turn strips of white paper dipped in protosulphate of 
manganese to brown, from the production of peroxyd of man- 
ganese. It will decolorize solution of indigo as promptly 
as nitric acid, and it bleaches even more powerfully than 
chlorine. This body, Schonbein, its discoverer, regards now 
as an allotropic condition of oxygen, (as suggested by Berze- 
lius.) Its presence in the air is shown by the discoloration 
of papers dipped in iodid of starch solution. It has been 
argued, but on insufficient grounds, that this body in the 

278. How is the lamp flame affected ? How does it act on life ? How 
on the blood ? 279. What of ozone ? How obtained ? What its cha- 





lir was a miasmatic agent. A few words will be in plac* 
here, upon the 

Management of Gases. 
280. Pneumatic Troughs. — Gases not absorbed by water, 

are always collected in 
a vessel of water, called 
a pneumatic trough. 
Figure 214 shows a 
small neat one, mado 
of glass, proper for the 
lecture-table ; but, for 
general purposes, they 
are usually made, like 
the one below, (fig. 
215,) of japanned cop- 
per, of tin plate, or of 
wood, to hold several 
gallons of water. The 

Fig. 214. 

essential parts are the well W, in which the air-jars are 

filled, and a shelf S, 
covered with about an 
inch of water. A 
groove or channel d 
is made in the shelf, to 
allow the end of the 
gas-pipe to dip under 
the air-jar. If nothing 
better is at hand, a 
common wooden tub or 
water-pail, with a per- 
forated shelf and invert- 
ed funnel, will answer for small operations. Learners are 
sometimes puzzled to tell why the water stands in an air- 
jar above the level of the cistern. A moment's thought, 
however, on the principles of atmospheric pressure (27) 
already explained, will make this clear. We must remem- 
ber, too, that gases are only light fluids, and must be pour- 
ed upward in water, by the same laws which require fluids 
heavier than air to be poured downward. 

281. To store large quantities of gases, capacious vessels 

280. What is a pneumatic trough ? How are gases managed ? How 
poured ? 281. How are they stored ? 

Fig. 215. 






of copper or tinned iron are used, which are called gas- 
holders. These vessels are made frequently to hold 30 to 
50 gallons. The simplest form is that of a large air-jar, pro- 
vided with stopcocks at the top for the entrance and escape 
of the gas, and contained in an exterior cylindrical vessel of 

water. A more con- 
venient gas-holder for 

some purposes is that 
s contrived by Mr. Pepys, 

a view and section of 

which are shown in the 

annexed figures, (216 

and 217.) It is a tight 

cylinder of copper or 

tin g, with a shallow 

pan of the same metal, 

supported above it by ' 
Fig. 21G. several props, two of Fi £- 2l7 - 

which are tubes with stopcocks, a b. Near the bottom is 
a large orifice o, for receiving the gas. To use this instru- 
ment, it is first filled with water by closing the lower orifice 
a with a large cork, and opening all the upper ones 
a b s. Water is then poured into the shallow pan ' p } 
until it runs out at s, which is then closed; the remain- 
der of the air escapes through b; when it is full, the 
cocks a b are shut, and the lower orifice being then opened, 
the water, sustained by the pressure of the air, cannot 
escape except as it is driven out by the entrance of the gas 
at o, from which it runs as fast as the gas enters. When 
used, arrangements must be made to 
provide for the water driven out by the 
gas entering at o. The gas is obtained 
for use by drawing it off from the orifice 
* or b at the same time that the 
shallow pan p is full of water, and the I 
cock a open. The tube to which 
this cock is attached goes nearly to the 
bottom of the vessel. An air-jar is 
easily* filled with gas from the holder 
by placing it full of water in the upper 

Fig. 218. 

Explain figures 216 and 217. 
Explain figure 21S. 

How is gas drawn from the gas bolder I 




pan, (see fig. 218,) over the orifice b; on turning the twc 
stopcocks a by the gas issues from b and fills the jar, while 
the water of the jar runs down the pipe a to supply the 
place of the gas. 

In collecting gas, the precaution should never b» neglected 
of first allowing all the atmospheric air to escape from the 
vessels, before any of the gas is saved for use. 

Bags of vulcanized India-rubber cloth aro prepared by 
the instrument-makers as gas-holders, which can be used 
without the inconvenience of employing water. They are 
filled by the flexible pipe p and stop- 
cock c, (fig. 219,) which also serve for 
the exit of the gas. 

Gases which are absorbed by water 
may be collected over mercury; the 
' high price of mercury makes, however, 
Fi 219 fc kis an expensive method ; moreover, 

some gases — as chlorine, for instance — 
act chemically on the mercury. We may better collect the 
absorbable gases in clean dry vessels, by displacement of 
air, as is explained in the next section. 



Equivalent, 35-50. Symbol, CI. Density, 244. 

282. History and Preparation. — This very remarkable 
element was first noticed by Scheele, in 1774, while examin- 
ing the action of chlorohydric acid on peroxyd of manga- 
nese. For a long time it was believed to be a compound 
body. It was called chlorine by Davy, who established its 
elementary character. 

It is easily obtained from chlorohydric acid HC1, by its 
action upon pulverized oxyd of manganese, in an apparatus 
similar to figure 220. The acid is poured in at pleasure by 
the safety tube s, after the manganese has been made into 
a paste with the first portions. The heat of a lamp or a 
an of coals evolves the gas freely. It is rapidly absorbed 
y cold water; but if the vessels are filled with water of 

What of India-rubber bags? What of absorbable gases ? 282. When 
and by whom was chlorine discovered ? How is it obtained ? How is it 






Fig. 220. 

Fig. 221. 

100° to 150° temperature, it is collected with little loss. 
Any acid vapors are washed out in w. A strong solution of 
common salt (brine) does not absorb chlorine, and may be 
usefully employed in some cases to collect this gas in a small 
porcelain or other trough. Owing to its great weight, it may 
also be very conveniently collected by displacement of air 
in dry vessels, using an apparatus like figure 221. The fluc- 
tuations of the air are prevented by a bit of card-board with 
a slit on one side, and the greenish color of the gas enables 
the operator to see when the vessel is full. The vessels 
must have glass stoppers or covers of glass ground tight; 
in such, the gas may be preserved at pleasure. The opera- 
tion should be performed in a well-ventilated apartment, 
to avoid injury from the corrosive and irritating gas. 

283. In this process the affinities are between the man- 
ganese, for one equivalent of the chlorine in the acid, form- 
ing chlorid of manganese, and between the oxygen of the 
manganese and the hydrogen of the acid, forming water 
The following symbols will render this more clear : we take 
MnO, and 2HC1, and obtain MnCl, 2HO, and CI. 

How by figure 221 ? What precaution is advised? 283. What art 
the affinities in this process? Give the equation. 






The last equivalent of chlorine, having nothing to detain 
it, is given off. 

Pure chlorine is also easily obtained by acting on one 
part of powdered bichromate of potash, in a small retort, 
with six parts of strong hydrochloric acid. A gentle lamp- 
heat is required to begin the process, which then goes on 
without further application of heat, yielding abundance of 

Dry chlorine is 
obtained by using 
an apparatus, figure 
222, attached to 
the evolution flask 
fig. 220 by o} any 
acid vapors are 
washed out in the 
bottle w, and all 
moisture is removed 
by the chlorid of 
Fig. 222. calcium tube a b, the 

dry gas being collected by displacement in /. 

284. Properties. — Chlorine is a greenish-yellow gas, 
(whence its name, from chloros, green,) with a powerful and 
suffocating odor. It is wholly irrespirable and poisonous. 
Even when much diluted with air, it produces the most 
annoying irritation of the throat, with stricture of the 
chest, and a severe cough, which continues for hours, with 
the discharge of much thick mucus. The 
attempt to breathe the undiluted gas would be 
fatal ; yet, in a very small quantity, and dis- 
solved in water, it is used with benefit by pa- 
tients suffering under pulmonary consumption. 
For this purpose an inhalation apparatus is 
used, like fig. 223. The mouth is applied at 
o, the air enters at a, and, passing through the 
dilute solution, becomes more or less charged 
with chlorine. Cold water recently boiled ab- 
sorbs about twice its bulk of chlorine gas, 
Fig. 223. acquiring its color and characteristic pro- 
perties. This solution is much used in the laboratory in 

How is it obtained dry ? 284. What are its properties ? How does it 
Affect respiration ? How is it safely inhaled ? 



id i 


preference to the gas. It should be preserved in a blue 
bottle, or in one covered by black paper, to avoid decompo- 
sition, (228.) The moist gas exposed to a cold of 32° yields 
beautiful yellow crystals, which are a definite compound 
of one equivalent of chlorine and ten of water, (C1,10HO.) 
Tf these crystals are hermetically sealed i 

up in a glass tube, (fig. 224,) they will, 
on melting, exert a pressure of five atmo- 
spheres, so as to liquefy a portion of the 
gas, which is distinctly seen as a yellow Fi g- 224 - 

fluid, of density 1*33, not miscible with the water which is 
present. It does not solidify at zero. Chlorine is one of 
the heaviest of the gases, its density being 2-44, and 100 
cubic inches weighing 76*5 grains. 

285. Chlorine solution readily dissolves gold-leaf, forming 
chlorid of gold : silver solution produces in it a dense pre- 
cipitate of chlorid of silver, which ammonia re- 
dissolves. A rod a, (fig. 225,) moistened in 
ammonia water, and held over chlorine solution, 
produces a dense cloud of chlorid of ammonium. 
A crystal of green vitriol dropped into a test- 
tube containing chlorine water, gives a dark so- 
lution at bottom of perchlorid of iron. Fi «- 225 - 

286. The bleaching power of chlorine is one of its most 
remarkable and valuable properties. The solution of chlo- 
rine immediately discharges the color of calico rags or of 
writing-ink. The moist gas does the same, but the dry gas 
does not bleach. Chlorine is evolved in the arts from a 
mixture of salt, sulphuric acid, and manganese, for the 
bleaching of paper and rags, and of all manner of cotton or 
linen stuffs. It does not bleach woollens, nor printers' ink, 
probably because of its indifference to carbon, which forms 
the basis of printers , ink. The bleaching power is probably 
due to its affinity for hydrogen. 

287. Chlorine spontaneously inflames- phosphorus, and 
powdered metallic arsenic, or antimony, forming chlorids of 
those substances. A rag or bit of paper, wet with oil of 
turpentine and held in a bottle of chlorine, is inflamed, and 

What of its solution? How crystallized? How liquefied? How 
donee? 285. What are tests for chlorine? 286. What valuable pro- 
perty of CI is named ? How if dry gas is used ? How is it evolved in 
the arts ? What exceptions to its bleaching ? Whence this property J 
287. How does CI act on phosphorus, Ac. ? How on oils ? 




the interior of the vessel is coated with a bril- 
liant black varnish of carbon, derived from the 
oil. A candle lowered into a vessel of chlorine, 
(fig. 226,) is slowly extinguished, with the escape 
of a dense volume of smoke. In these cases, 
the action is between the chlorine and the hydro- 
gen of the organic substances. The disinfection 
of offensive apartments, sewers, and other like 
Fig. 226. pjjuj^ j S rapidly accomplished by chlorine and 
the " bleaching powders." 

288. Double Condition, or AUotropism of Chlorine. — 
Chlorine exists both in an active and a passive state. 
The first is its condition as ordinarily known, when pre- 
pared in daylight. If an aqueous solution of chlorine 
be prepared as before mentioned, in recently boiled water, 
and a part of it be exposed in an inverted bulb to the 
direct rays of the sun, or a strong daylight, while another 
portion, as soon as prepared, without exposure to light, is 
set aside in a dark closet, and in a similar vessel, we shall 
find them very differently affected. That which was in the 

dark will have undergone no change, while that in 
the sunlight will have suffered decomposition ; a 
notable quantity of nearly pure oxygen will have 
collected in the bulb, as shown in fig. 227, and 
chlorohydric acid will have been formed in the fluid, 
from the union of the chlorine and the hydrogen of 
the water, whose oxygen is set free. The rapidity 
Fig. 227. f tbj s decomposition of water by the chlorine, de- 
pends on the intensity of the sun's rays, and the tempera- 
ture, and being once begun, it continues afterward even in 
the dark. The indigo rays (76) are chiefly instrumental in 
producing this effect. (Draper.) 

Compounds of Chlorine with Oxygen. 

289. Chlorine and oxygen have no disposition to unite, 
under any circumstances, directly; but numerous com- 
pounds of these two elements are produced indirectly, of 
which we tabulate five, as follows : — 

How on a candle ? Whence this peculiarity? What of disinfection f 
28S. How does light affect chlorine ? Illustrate by fig. 227. , What ray 
effects this ? 






Hypochhrous acid CIO 

Chlorous acid CIO. 

Hypochlorio acid, (peroxyd of chlorine,) C10 4 

Chloric acid CIO. 

Hyperchloric acid , C10 t 

As the most simple method, we commence with — 

290. Chloric Acid j (C10 5 ). — This most important com- 
pound of chlorine and oxygen is formed when a current of 
chlorine is pasaed through a solution of potash, to saturation. 
On evaporating this solution, flat tabular crystals of a white 
salt are gradually formed, which are chlorate of potassa, 
while chlorid of potassium remains in the solution. The 
reaction is between 6 equivalents of chlorine and 6 of 
potassa, forming 5 of chlorid of potassium and I of chlorate 
of potassa; thus, 6C1+6K0=5KC1+K0,C10 5 . Chloric 
acid Is obtained separate with some difficulty, by decom- 
posing a solution of chlorate of baryta by the requisite 
amount of sulphuric acid, and gradually evaporating the 
filtered liquid to a syrup. In this state its affinity for all 
combustible matter is so great, that it cannot be kept in 
contact with any substance containing carbon or hydrogen. 
Paper moistened by it takes fire as it is dried. The chlo- 
rates are recognized by their powerful action on combustible 
matter, by yielding pure oxygen when heated, and by 
giving out the yellow chlorous acid when treated with 
sulphuric acid. 

291. HypocKLorous Acid, (CIO.) — This acid gas is ob- 
tained when a current of chlorine traverses a weak solution 
of potassa, when, if cold, no chlorate of potassa is formed, 
but a solution having most remarkable bleaching powers. 
It contains both chlorid of potassium 
and hypochlorite of potassa ; thus, 
2K0-|-2C1=K0,C10+KC1. It is ob- 
tained also by the agitation of chlorine 
with red oxyd of mercury, or better by 
passing dry chlorine over red oxyd of 
mercury, contained, as in fig. 228, in a 
horizontal tube 6, (shown only in part,) 
and condensing the evolved gas CIO in Fig. 228. 

289. Name the compounds of CI and 0. What arc their formulas? 
290. What is chloric acid? Ilow formed? What the reaction? What 
character has chloric acid ? What of its salts ? 291. What is hypo- 
valorous acid ? How obtained ? Give the reaction. Explain its produc- 
tion by fig. 227. 





the U tube, refrigerated by means of ice and salt in the 
outer vessel. Chlorid of mercury is formed, and oxyd 
of chlorine CIO. Hypochlorous acid is a light-yellow 
gas, much resembling chlorine; condensed, it is a reddish- 
yellow corrosive liquid, boiling at 68°, and sparingly 
soluble in water. The vapor detonates with a hot iron : water 
absorbs 200 times its volume of it, and gains a beautiful 
yellow color and powerful bleaching properties. Its aqueous 
solution is very unstable, being decomposed by light, and 
even by agitation with irregular bodies, as broken glass. 
Hypochlorous acid is one of the most powerful oxydizing 
agents known, raising sulphur and phosphorus to their 
highest state of oxydation — a result which only strong 
nitric acid can accomplish. It is formed from two volumes 
of chlorine and one of oxygen condensed into two volumes. 

2 volumes of chlorine weigh 4*880 

1 " oxygen " 1-105 

5985 -5-2 = 2-992 

while experiment gives us 2-977 for the density of this sub- 
stance. The euchlorine of Davy is a mixture of chlorine 
and chloro-chlorous acid, and not a protoxyd of chlorine, as 
was supposed. It is obtained when chlorohydric acid acts 
on chlorate of potassa, is a greenish-yellow gas, darker than 
chlorine, of a very pungent and persistent odor. It explodes 
with a hot iron. 

292. Chlorous, hy- 
pochloric, and jper- 
chloric acids are all 
procured from the' 
decomposition of 
chloric acid. When 
fused chlorate of 
potassa is acted on 
by sulphuric acid, 
in the vessel b, (fig. 
229,) a very explo- 
sive, yellow gas 
Fig. 229. collects in a. This 

What ore its characters? What is its volume, constitution, and den- 
sity ? What is euchlorine ? What of chlorous and hyperchlorous acids ? 




experiment demands great precautions to avoid accident. 
The vessel 6 may be secured by setting it into an outer 
vessel of warm water. The gas explodes by a warm iron, by 
pressure, and sometimes without any apparent cause. 

293. If strong sulphuric acid is poured upon a small 
quantity of crystals of chlorate of potash in a wine glass, a 
violent crackling is heard, and the glass is soon filled with 
the heavy yellow vapors of the chlorous acid gas, which at 
once inflame a rag held over it wet with turpentine, with a 
smart explosion. If chlorate of potash is mixed with sugar, 
(both separately pulverized and mingled with caution,) a drop 
of sulphuric acid will inflame the mixture with a brilliant com- 
bustion. Phosphorus burns spontaneously in chlorous acid 
gas : if some small fragments of phosphorus are added to a 
glass of water at the bottom of which a few crystals of 
chlorate of potash have been placed, (fig. 230,) 
and sulphuric acid is introduced by means of a 
long-tubed funnel to the bottom of the vessel, 
the salt is decomposed, and the phosphorus 
flashes under water in the chlorous acid which 
is set at liberty. Fig. 230. 

Equivalent) 80. Symbol, Br. Density, in vapor, 5*39. 

294. History. — This element was discovered in 1826, by 
M. Balard, in the mother-liquor, or residue of the evapora- 
tion of sea-water, and by him named from its offensive odor, 
(bromos, bad odor.) It is widely diffused in nature, exist- 
ing in minute quantities in combination with various bases 
in the salt-water of the ocean, of the Dead Sea, and of 
nearly all salt-springs. It is also found in a few minerals. 
The salines of our Western States are many of them rich 
in bromids. It has been largely prepared at Freeport, 
Pennsylvania, on the Ohio, for use in pharmacy. 

295. Bromine is a dense red fluid, exhaling at common 
temperatures a deep reddish-brown vapor. It is one of the 
heaviest non-metallic fluids known, its density being from 
2*97 to 3 187. Sulphuric acid floats on its surface, and is 

What precaution is given ? 293. What of sulphurio acid on chlorate 
of potassa ? What is the action on phosphorus ? 294. Give the history 
of bromine Where is it found ? 295. Give its characters. 




used to prevent its evaporation. At zero it freezes into a 
brittle solid. It boils at 116-5°. A few drops in a large 
8ask will fill the whole vessel, when slightly warmed, with 
blood-red vapors, which have a density of 5*39. It is a 
non-conductor of electricity, and huffers no change of pro- 
perties from heat or electricity. It dissolves slightly in 
water, forming a bleaching solution ; and at 32°, if left in 
contact with water, it forms a crystalline hydrate with it, of 
a red bronze color, analogous to the hydrate of chlorine. It 
is a corrosive and deadly poison, disorganizing organic struc- 
tures with great energy. One drop on the beak of a bird 
Produced instant death. It has even been used for suicide, 
ts odor resembles chlorine, but is more offensive and per- 
sistent. It has bleaching properties. In a word, bromine 
in all its properties and combinations, has the greatest ana- 
logy to chlorine, but is less energetic in its affinities, being 
displaced by chlorine from its combinations. 

Bromine acts with explosive violence on phosphorus, po* 
tassium, antimony, and other similar substances, forming 

296. Bromine is used in photography, and its compounds 
also in medicine. It is detected in the mother-liquor of 
salt-water by chlorine gas, or solution of chlorine, which 
sets it free, when it is recognized by its peculiar color. 
Ether added to this solution takes up the liberated bromine 
on agitation, and floats on the surface in a reddish-brown 
stratum. It is prepared in the arts by distilling a mixture 
of bromid of sodium, manganese, and dilute sulphuric acid, 
and collcpting the product in a cold receiver. 

Bromic acid Br0 5 is similar in all its reactions to chloric 
acid, and forms salts with alkaline bases, called broraates. 

The chloride of bromine BrCl s is soluble in water and de- 
composed by alkalies. 

Equivalent y 127. Symbol, I. Density in vapor, 8*7. 

297. History. — Like chlorine and bromine, this substance 
has its origin in the sea, being secreted by nearly all sea- 
weeds from the waters of the ocean. It was discovered in 

What smell has it ? How does it act on combustibles ? 296. How 
used ? How detected? What compounds does it form ? 297. What if 
llie history of iodine? 

, Digitized 


IODINE. 185 

1811, by M. Courtois, of Paris, in the kelp, or ashes of sea- 
weeds. The common bladder sea-weed, (fucus vesiculosa*,) 
and many other sea-weeds of our own coasts, abound in salts 
of iodine. It has been found in mineral springs associated 
with bromine, but less abundantly, and also in one or two 
minerals. In the arts its chief uses are for the photographic 
pictures, and in the process of dyeing. In medicine it is 
of great value, in glandular and other diseases. 

298. Preparation.— : Kelp is treated with water, which 
washes out all the soluble salts, and the filtered solution is 
evaporated until nearly all tho carbonate of soda and other 
saline matters have crystallized out. The remaining liquor, 
which contains the iodine, as iodid of magnesium, &o., is 
mixed with successive portions of sulphuric acid in a leaden 
retort, and after standing some days to allow the sulphu- 
retted hydrogen, &c, to escape, peroxyd of manganese is 
added, and the whole gently heated. Iodine distils over in 
a purple vapor, and is condensed in a receiver, or in a series 
of two-necked globes. 

299. Properties. — Iodine crystallizes in brilliant blue- 
black scales of a metallic lustre, somewhat resembling plum- 
bago. When slowly cooled from a state of dense vapor in 
a glass-tube hermetically sealed, it crystallizes in acute octa- 
hedrons with a rhombic base, (46.) The density of iodine 
is 4*95, it melts at 235°, and boils at 247°, forming a superb 
violet vapor of unequalled beauty; (hence its name, lodes, like 
a violet.) For this purpose a few grains of it may be vola- 
tilized in a bolt-head, or from a hot surface under a bell, as 

in fig. 231, when on cooling it is deposited 
in brilliant crystals lining the glass. It 
assumes the sphreoidal state in a red-hot 
crucible, forming a splendid experiment, 
(131.) It is almost insoluble, one part dis- 
solving in 7000 parts of water. Alcohol 
___^^_. dissolves it largely, forming tincture of 
"T! - T^"^ iodine. Sal-ammoniac, nitrate of ammonia, 
and soluble iodids also dissolve it. It tem- 
porarily stains the skin deep brown, and its odor reminds us 
somewhat of chlorine. 

300. Chlorine and bromine both decompose the com- 

In what is it found ? How prepared ? 299. What are its characters? 
What of its vapor ? How soluble ? What dissolves it? 




pounds of iodine. Iodine is an energetic poison. Iodine 
forms a beautiful deep-blue compound with a cold solution 
of common starch. By this test a millionth part of iodine 
can be detected. In combination it is detected by the same 
agent, if a little nitric acid or chlorine water is previously 
added to the fluid supposed to contain an iodid, whereby 
the iodine is set free. Acetate of lead added to solutions of 
salts of iodine produces a yellow crystalline precipitate. The 
iodid of potassium is the salt most familiarly known of all 
the iodine compounds, and is the usual form in which this 
substance is administered medicinally. 

Compounds of Iodine with Oxygen. 

301. Iodine unites with oxygen, forming hypoiodic, iodic, 
and hyperiodic acids. Their constitution is seen in the fol- 
lowing formulas : 

Hypoiodic acid I0 4 

Iodic acid 10, 

Hyperiodic acid IOi 

These acids are analogous to the hypochloric, chloric, and 
perchloric acids. Iodic acid is formed by the action of 
strong nitric acid on iodine, and subsequent evaporation, to 
expel the free nitric acid remaining. It is a very soluble 
substance, and crystallizes in six-sided tables. Chlorine 
unites with iodine, forming two, and possibly three distinct 
chlorids, (IC1, IC1 8 , and IC1 5 .) These are formed by the 
direct action of chlorine on dry iodine. There are also bro- 
mids of iodine of uncertain composition. 

Equivalent, 19. Symbol, F. Density, (hypothetical,) 1-292 

302. This element is known entirely by its compounds 
Its remarkable energy of combination with other elements, 
and especially with silicon, which is a constituent of all 
glass, has rendered its isolation very difficult. It is a yel- 
lowish-brown gas, having the smell and bleaching proper- 
ties of chlorine. It does not act on glass, (as its compound 
with hydrogen does,) but unites directly with gold. Its 
specific gravity is 1-292. 

Fluorine forms no compound with oxygen, and probably 

300. Give tests for iodine. Give its oxygen compounds ? 302. What 
vf fluorine ? Why is it difficult to isolate ? 




holds a place intermediate between oxygen and chlorine. 
Its most remarkable compound, fluohydric acid, we shall 
mention in the section on hydrogen. Its power of etching 
glass was known long before fluorine was suspected to 

303. When a mixture of fluor-spar with peroxyd of man- 
ganese and sulphuric acid is heated, a reaction takes place, 
by which fluorine in an impure form is disengaged. If the 
gas thus produced is passed through water having iodine sus- 
pended in it, combination takes place, and a fluorid of iodine 
is formed, which crystallizes in yellow scales. A fluorid of 
bromine is formed by a similar process, which has been used 
iTVthe photographic art with success. It is not crystallizable. 
The precise composition of these bodies is not known 

The atomic weight of fluorine is very nearly an aliquot 
part of the equivalents of chlorine, bromine, and iodine, and 
these four bodies form a well-marked natural family, closely 
related by many similar properties. 


Equi valent, 16*0. Symbol, S. Density in vapor , .6*654. 

304. History. — Sulphur is one of those elements which, 
occurring abundantly in nature, have been known from the 
remotest antiquity. It is found in many volcanic regions, 
as in the Island of Sicily, the vicinity of Naples, in Cuba, 
and many islands of the Pacific. Recent volcanic regions 
producing sulphur are called solfataras. It is also found 
in beds of gypsum, as a rock, near Cadiz in Spain, and at 
Cracow in Poland. Sulphurets of iron, copper, and other 
metals are widely diffused in the earth ; and in combination 
as sulphuric acid, sulphur forms nearly half of the weight 
of Common gypsum, or plaster of Paris. 

305. Properties. — It is a straw-yellow, brittle solid at 
common temperatures, having a gravity of 1*98. It is 
tasteless, and without odor until rubbed. By warmth and 
friction it acquires its well-known brimstone odor. It is a 
non-conductor of heat and electricity. By friction it gives 

How is fluorine disengaged ? What of its atomic weight ? 304. What 
ii the history of sulphur ? 305. What are its equivalent and characters ? 





negative electricity abundantly. It is very volatile, subliin- 
ing in " flowers of sulphur" — minute crystals — even below 
the melting point, or 226°. By this means it is freed from 
earthy and other impurities. When fused below 280° it is 
an amber-colored mobile fluid, lighter than solid sulphur, 
which sinks in it. It is cast in moulds, giving roU sulphur. 
On cooling, it shrinks so as to fall from the mould, (fig. 232.) 
The roll sulphur held for a moment in the hand 
gives a peculiar crackling sound, from the disturb- 
ance of its particles by heat, and it often breaks 
when so held. It is insoluble in water, and nearly 
so in alcohol and ether. In oil of turpentine and 
some other oils, it is partly soluble, and largely fio 
in bisulphid of carbon. Vapor of alcohol also dis- 
solves sulphur vapor. 

Sulphur is very combustible, burning with a 
blue flame and the familiar odor of a match, due 
to the production of sulphurous acid. It combines 
energetically with metals, forming sulphurets or 
sulphids, supporting combustion like oxygen. 
Fig. 232. Thus, a bundle of iron wires, as shown by Dr. Hare, 

Fig. 233. 

Fig. 235. 

Fig. 234. 

(fig. 233,) is rapidly burned with scintillations, when held 
in the jet of sulphur vapor i» uing from a gun-barrel, the 
end of which has been heated to redness, bits of roll sul- 
phur thrown in, and the muzzle stopped with a cork. 

306. Sulphur occurs in two distinct crystalline forms, 
one of which is the right rhombic octohedrdn and the other 
is the oblique rhombic prism. Figures 234 and 235 give its 
usual form as found in nature or as crystallizing from solution. 
When slowly cooled from fusion, as in a crucible, if the 
crust formed on the surface be pierced while the interior is 

How is it purified ? How does heat affect it ? What solubility has it f 
How does it act on combustibles ? What is Hare's experiment ? 306. 
What of ths form of sulphur ? 




still fluid, and the liquid part turned out, 
the interior will present, as in fig. 236, 
long, slender, compressed prisms. These 
belong to the second form of sulphur. 
This was one of the first instances of 
dimorphism noticed by Mitscherlich. 

307. The fusion of sulphur at different 
temperatures presents remarkable facts. w „«- 
At 226°-280° it is a clear, straw-yel- W™- 
low fluid ; before reaching 280° it begins to grow darker ; 
from that point to 300° it assumes a deep yellow color; at 
374° it has an orange tint and becomes somewhat viscid ; 
at 500° it becomes dull-brown, and at this high temperature 
its viscidity is such that the vessel containing it may be 
turned over without the sulphur falling out. Above this 
last temperature it begins to grow more fluid. If at this 
moment it is thrown into cold water, it remains pasty, trans- 
parent, preserves its brown color, and may be drawn out 
into long threads which have almost the elasticity of 
caoutchouc. It regains its original brittleness only after 
many hours. In this pasty state, sulphur may be moulded 
by the hands, and is used to copy medallions and other 
works of art. At 600° it is volatilized in a deep red-brown 
vapor, resembling the vapor of bromine. The density of 
its vapor is 6 # 654. 

308. In its chemical relations, sulphur much resembles 
oxygen. It forms sulphurets with most of the elements that 
form oxyds, and these sulphurets often unite to form bodies 
analogous to salts, as the oxyds do. Berzelius insists, very 
properly, that its binary combinations, from their analogy 
to the oxyds, should be called sulphids y and not sulphurets. 

Its uses are well known. It is one of the essential ingre- 
dients of gunpowder, and is the basis of matches of all 
kinds. Nearly all the sulphuric acid used in the arts is 
made from it. The gas arising from its combustion is em- 
ployed in bleaching straw and woollen goods ; and in medi- 
cine it has a specific power in certain obstinate cutaneous 

The flowers of sulphur of commerce nearly always have an 
acid reaction, due to the sulphurous acid formed in subliraa- 

Hcw is it obtained crystallized ? 307. Give the facts observed in its 
fusion. What of its vapor? 308. What are tho relations of sulphur ? 
What its uses? 





tion. All the sulphur of commerce is obtained from iln 
ores by sublimation in large chambers, — or, when cast in 
blocks, by distillation and fusion in earthenware pots. 

Compounds of Sulphur with Oxygen. 

809. The compounds of sulphur and oxygen are nume- 
rous, but only two of them will engage our attention at 
present, namely: 

Sulphurous acid SO« 

Sulphuric acid SO, 

The other compounds of sulphur and oxygen are ex- 
pressed by the formula S 9 9 , S 9 5 , S,O s , S 4 s , S s O s . 

310. Sulphurous Acid, S0 9 . — Preparation. — This is the 
sole product of the combustion of sulphur in oxygen, as in 
the experiment figured in fig. 237, where burning sulphur 

Fig. 237. 

Fig. 238. 

in a spoon is lowered into a jar of oxygen gas. Other 
methods are used however in the laboratory to procure this 
gas. One of the best is to heat in a retort or flask (fig. 
238) an intimate mixture of six parts of peroxyd of manga- 
nese and 1 of flowers of sulphur, in fine powder. The sul- 
phur is burned at the expense of one portion of the oxygen 
of the peroxyd of manganese. The sulphurous acid gas 
is given off abundantly, and may be freed of a little vo- 
latilized sulphur, by a wash-bottle. Mercury and copper 
also decompose sulphuric acid, yielding sulphurous acid, by 
aid of heat ; but the first method is much preferable on 
every account. It must be collected in dry vessels or over 

309. What are its oxygen compounds? 
prepared in fig. 237 ? How collected ? 

310. What is SO.? How 





811. Properties. — Sulphurous acid is a colorless acid gas, 
with a pungent^ suffocating odor, recognized as that of a 
burning match. It extinguishes flame, A lighted candle 
lowered into a jar containing it is extinguished, and the 
edges of the flame, as it expires, are tinged with green. 

A solution of blue litmus or purple cabbage turned into 
a jar of the gas is at first reddened by the acid, and then 
bleached. Articles bleached by it, after a time regain their 
previous color. Water at 60° absorbs nearly fifty times its 
volume of sulphurous acid, forming a strongly acid fluid. 
Hence the necessity for collecting this gas over mercury, or 
by displacement of air in dry vessels. Its avidity for mois- 
ture is so great that it forms an acid fog with the water in 
the atmosphere, and a bit of ice slipped under a jar of it 
on the mercurial cistern is instantly melted; the water ab- 
sorbs the gas, and the mercury rises to fill the jar. 

312. Sulphurous acid is easily liquefied . under ordinary 
pressures at 14° and below, using a tube with a bulb E, like 

fig. 239, placed in a refrigerating vessel 
F. The gas is first dried by chlorid of 
calcium before passing into E. The 
liquid gas is easily preserved by turn- 
ing it into a tube drawn out like A B, 
f fig. 240,) and previously refrigerated, 
the part A serves for a funnel. The 
' blowpipe flame seals it hermetically at 

F* 239 a ' an( * * fc ma ^ k® ^ en P reserve( ^ f° r 
lg ' * future use. Under a pressure of two 

atmospheres, this gas is condensed at a temperature Fig. 240. 
of 59°. It is a colorless mobile fluid of a density of 1*42. 
Its evaporation produces intense cold. If the ball of a 
mercury thermometer is enveloped in cotton and moistened 
by liquid sulphurous acid, the mercury is frozen, and a spirit 
of wine jbhermometer indicates a temperature as low as 
— 60°. By its evaporation water is frozen in a red-hot cru- 
cible. It is a crystalline solid, transparent and colorless, at 
105°, sinking in the liquid gas. 

313. The volume of sulphurous acid is the same as that 
of the oxygen employed in producing it. In other words, sul- 


311. Give its properties. What of its bleaching? Of its avidity for 
moisture? 312. llow and at what temperature liquefied? How collected 
and preserved ? What of its sudden evaporation ? What temperaturo ? 
313. What of the volume of SO*? Give the calculation. 




phurous acid contains 1 volume of oxygen and £ volume 
of sulphur yapor (258) condensed into 1 volume. Thus, 

One volume of sulphurous acid density 2*247 

6ub8tract the weight of 1 volume of oxygen 1*106 

Leaving 1*141 

Which represent! very nearly |th volume of sulphur 

vapor=?*5! M09 


By weight, sulphurous acid contains sulphur 50*87, 
oxygen 49*13 = 100. One hundred cubic inches of it 
weigh 68*70 grains. 

3 14. Besides its use in bleaching straw and woollen goods, 
sulphurous acid is employed as a bath for diseases of the 
skin, and is a powerful disinfectant, even arresting putrefac- 
tion and fermentation. 

Sulphites are salts containing sulphurous aoid. Their 
solutions are gradually changed to sulphates by absorbing 

815. Sulphuric acid, SO s .HO. — This acid is one of the 
most important compounds known ; its affinities are very 
powerful, and no class of bodies is better understood by 
chemists than the sulphates. In the arts great use is made 
of sulphuric acid, many millions of pounds of it being an- 
nually consumed in manufacturing nitric and muriatio 
acids, the sulphates of copper and alum, in the process of 
dyeing, and more than all, in the manufacture of carbonate 
of soda from sea-salt. 

It is not formed by the direct union of its elements, since 
we have seen that only sulphurous acid can result from the 
combustion of sulphur in oxygen. Sulphurous acid must 
be oxydized to form sulphuric acid. 

316. This may be done by passing a mixture of sulphur* 
ous acid with common air over spongy platinum, heated to 
redness in a tube, when there will issue from the open end 
of the tube a mixture of sulphuric acid in vapor, with ni- 
trogen from the air. In the arts, however, this process 
cannot be used *, but sulphuric acid is made on a large scale 
by bringing together sulphurous acid SO s , hyponitrio 
acid N0 4 , and water HO, all in a state of vapor, in a large 
chamber, or series of chambers, lined with lead, when sul- 

What of its density ? 314. What of the uses of sulphurous aoid ? 311b 
What of SO. ? What it* use ? 316. How is SO, formed ? 





Fig. 241. 

phntous acid SO fl passes to a higher state of oxydation 
SO s at the expense of one-half the oxygen of the hypo- 
nitric acid N0 4 , which thus becomes reduced to the state 
of the deutoxyd ■ .% 

ofmtrogen,(NO fl .) ]fl 

The arrangement I ml P 

employed is repre- 
sented in fig. 241 . 
A A is a chamber, 
fifty feet or more 
long, lined on all 
aides with sheet- 
lead. A very large 
leaden tube B, 
opening into one 
end of the cham- 
ber, communicates 
with a furnace. Its lower end rests in a gutter 00 of 
dilute acid, to prevent the effects of too much heat and the 
escape of the vapors. The sulphur is introduced by a door 
c to an iron pan; and a fire built beneath, n. The heat 
melts the sulphur, which burns in a current of air passing 
over it, and the sulphurous acid thus formed enters the 
chamber, in company with air, and the vapors of nitric and 
hyponitric acids set free from small iron pans standing over 
the sulphur, and containing the materials to evolve nitric acid, 
(sulphuric acid and saltpetre.) A small steam-boiler e 
furnishes a jet of steam x as required, and a quantity of 
water, covers the floor, which is inclined so as to be deepest 
at h. A chimney with a valve or damper p allows the 
3scape of spent and useless gases. Things being thus ar- 
ranged, the chamber receives a constant supply of sulphur- 
ous acid, common air, nitric acid vapor, and steam. 

317. These compounds react with each other in such a 
manner that the oxygen of the air is constantly transferred 
to the sulphurous acid, to form sulphuric acid. Deutoxyd 
of nitrogen NO, in contact with air becomes hyponitric acid 
N0 4 , and this last in presence of a large quantity of water is 
transformed into nitric acid N0 5 and deutoxyd of nitrogen. 
Thus, 6N0 4 +»H0 =4N0 5 +nHO+2NO r Now, sulphur- 
ous acid, in presence of hydrated nitric acid (N0 5 +wHO) 

Explain the fig. 241. 317. Whence the oxygen to form SO* ? Give 
the reactiona by the formula?. 

♦ 13 





is changed into sulphuric acid, and transforms the nitric acid 
into hyponitric acid, thus renewing the reaction continually. 
Thus, S0 a +N0 5 +»H0=S0 8 +nH0+N0 4 . In this way 
a small quantity of nitric acid can he made to oxydize an 
indefinite amount of sulphurous acid ; serving the purpose, 
as it were, of a carrier of oxygen from the atmospheric air 
to the sulphurous acid. Meanwhile the water on the floor 
of the chamber grows rapidly acid ; and when it has attained 
a specific gravity of about 1 # 5, it is drawn off and concen- 
trated by boiling, first in open pans of lead until it becomes 
strong enough to corrode the lead, and afterward in stills 
of platinum until it has a density of about 1*8, in which state 
it is sold in carboys, or large bottles, packed in boxes. 

318. The process of forming sulphuric acid is easily 
illustrated in the class-room by an arrangement of apparatus 
like that shown in fig. 242. Two flasks b e are so connected 

Fig. 242. 
by bent tubes with a large balloon, that from one b sulphurous 
acid, and from the other e deutoxyd of nitrogen are supplied 
to the large balloon r. A third flask to furnishes steam as it 
is wanted. Fresh air must be occasionally blown in at the 
open tube t, the effete products escaping at o. Thus arranged, 
the reactions above described take place. If but little vapor 
of water is present, the sides of the globe are soon covered 

What is the density of SO, in the chambers ? 318. Explain the figur* 
and process 242. 




with a white crystalline solid, which appears to be a compound 
of sulphurous and of nitrous acids (S0 fl ,N0 4 .) This sub- 
stance is decomposed by a larger quantity of water into sul- 
phuric acid and hyponitric acid, and as it is known . to be 
formed in the leaden chambers in large quantities, it is sup- 
posed to have an important influence in the production of sul- 
phuric acid. 

319. This process by the leaden chambers is known in 
the arts as the English process for sulphuric acid. Formerly 
sulphuric acid was procured by distilling dry sulphate of 
iron (green vitriol) in earthenware retorts, at a high tem- 
perature. The oily fluid thus obtained was hence vulgarly 
called oil of vitriol. This old process is still in use at Nord- 
hausen, in the Hartz Mountains, producing an acid which is 
commonly known as Nordhausen acid. It is the most con- 
centrated form possible for fluid sulphuric acid. Sulphuric 
acid unites with water in four proportions, forming definite 
compounds, namely : 

Nordhausen acid, sp. gr. 1*9 2(SO,)HO 

Oil of vitriol, " 1-83 SO„HO 

Acid of " 1-78 SO„HO+HO 

Acid of " 1-63 SO*HO-f-2H 

320. Nordhausen acid is a dark-brown, oily fluid, fum- 
ing when exposed to air, and hissing like a hot iron when 
water is let fall into it drop by drop. To mingle the two 
rapidly in any quantity is unsafe. Cautiously heated in a 
retort protected by a hood of earthenware A, as in fig. 243, 

Fig. 243. 

319. What is this process called ? What was the old one? Whence 
the vulgar name ? What is the most concentrated SO, ? What hydrate* 
tf SO, ? What of Nordhausen SO, ? 




a white, crystalline, silky product distils oyer and is col* 
lected in the cool receiver. This is anhydrous sulphurio 
acid S0 8 . It does not possess acid properties by itself, but 
by contact with water or moisture it is changed to common 
sulphuric acid. It must be preserved in tubes hermetically 
seated. It has therefore been inferred that sulphuric acid 
cannot exist without water, or that water is essential to the 
acid property. In this case it is supposed that the oxygen 
of the water joins that already with the sulphur, (forming 
S0 4 ,) while the new compound thus produced unites with 
hydrogen, forming S0 4 H. 

321. When exposed to a temperature of — 29°, sulphurio 
acid freezes; and acid of 1*78 exposed to a temperature of 
82° freezes in large crystals. One hundred parts of concen- 
trated sulphuric acid contain 81 64 real acid, 18 36 water, 
80 8 HO. At 620° it boils, giving off a dense, white, and very 
suffocating vapor. It is intensely acid to the taste, and 
deadly, if by any accident it is swallowed, corroding and 
burning the organs with intense heat. It blackens nearly 
all inorganic matters, charring or burning them like fire. Its 

strong disposition for water enables 
us to employ it in desiccation, and 
in the absorption of aqueous 
vapor; using for this purpose a 
shallow pan (fig. 243) containing 
Fig. 244. S0 8 HO, while the substance to be 

dried is placed above it, and the whole then covered with a 

low bell-jar or a tight-fitting plate. 

322. Great heat is generated from the mixture of 4 parts 
by weight of strong sulphuric acid and 1 of water, and a 
diminution of bulk attends the mixing. The temperature 

rises as high as 200°. So that water in a test tube 
b (fig. 245) may be made to boil when placed in 
the mixture contained in the beaker-glass a. If 
common sulphuric acid is used for this purpose, it 
becomes milky when water is added to it, from the 
precipitation of sulphate of lead, derived from the 
lg * ' boilers in which it was made. This salt is soluble in 

strong sulphuric acid, but is precipitated by addition of 


How is crystalline SO, obtained? What formula is given? 321. 
When does SO, freeze ? What of sp. gr. 178 ? Give other traits of SO* 
522. What if water and SO, are mingled ? Why is the mixture milky ? 





323. Sulphuric acid forms sulphates, a class of salts most 
minutely known to chemists, and many of which are fami- 
liarly known in common life. 

Chloride of barium, added to sulphuric acid, or to a soluble 
•sulphate, throws down an abundant precipitate of sulphate 
of baryta, a salt insoluble in all menstrua. The same test 
gives a precipitate also with sulphurous acid, (sulphite of 
baryta,) but the latter is soluble in chlorohydric acid. 

324. There are several chlorids of sulphur. The apparatus 
figured in fig. 245 shows the manner of preparing one of 

Fig. 246. 

them C1S 9 . Sulphur is placed in the small retort P and 
fused by the lamp beneath, while a current of chlorine libe- 
rated from the ballon c, and dried over the chloride of cal- 
cium tube a, is delivered gently by the descending tube almost 
in contact with the fused sulphur in P. Combination en- 
sues, chloride of sulphur distils over and is condensed in the 
receiver r, kept cool by water from the fountain. This 
chlorid of sulphur is a reddish-yellow fluid, of a disagreeable 
odor. It boils at 280°, giving a vapor of density 4*668. 
The density of the liquid is 1*68. Water decomposes it, 
forming sulphur and chlorohydric acid. One volume of this 
substance in vapor is formed of 

1 toL chlorine 2*440 

i " sulphur °-f* 2-218 

Giving the theoretical density 4*658 

While experiment gives 4*668 

323. What salts does SO. form? What tests for SO.? 324. ETow it 
CIS, formed? Describe fig. 245. What are its characters? Give its 
volume and density. 




The bromids and iodids of sulphur possess very little 

Equivalent, 40. Symbol, Se. Density, 4-3. 

325. History and Properties. — This element was dis- 
covered by Berzelius, in 1818, and named by him from 
selene, the moon. It is associated in nature with sulphur 
in some kinds of iron pyrites, and in a lead ore from 
Saxony, and also at the Lipari Islands combined with sul- 
phur and accompanied by other volcanic products. 

It closely resembles sulphur in most of its properties, as 
well as in its natural associations. At common tempera- 
tures it is a brittle solid, opake, and having a metallic lustre 
like lead, but in powder it is of a deep red color. Its 
specific gravity is 4-28 for the vitreous, and 4-80 for the 
granular variety from slow cooling. It softens at 212°, 
and may then be drawn out into red-colored threads ; at a 
little higher temperature it melts completely, and boils at 
650°, giving a deep yellow vapor without odor. It passes 
through the same changes of state by heat as sulphur. It 
is insoluble. When heated in the air, it combines with 
oxygen, and gives out a disagreeable and strong odor, like 
putrid horse-radish. Before the blowpipe, on charcoal, it 
burns with a pale blue flame, and ^ of a grain, so heated, 
will fill a large apartment with its odor. It is a non-con- 
ductor of heat and of electricity, and excites resinous elec- 

326. The compounds of selenium with oxygen are three, 
two of which are acids, analogous to sulphurous and sul- 
phuric acids. They are — 

Oxyd of selenium SeO 

Selenious acid SeO* 

Selenic acid SeO t 

Oxyd of selenium is formed when selenium is heated in 
the air. It is a colorless gas, and possesses the strong odoi 
before mentioned. 

327. Selenious acid is formed when selenium is burned 

325. What of selenium? Give its characters. Its equivalent 326 
What compounds of has it ? 




in a current of oxygen gas, as in the tube a, (fig. 247.) A 
small portion of selenium is placed at b, 
and fused by a lamp ; at this temperature, 
oxygen flowing, from a reservoir, in sit a, 
combines with the selenium, forming SeO B , 
which is a white crystalline body, very so- 
luble in water, and sublimed by heat un- 
changed. Selenic acid is formed when sele- 
nium is burned by nitrate of potash, formiDg ^ 
selenate of potash. It resembles sulphuric % 
acid in its properties. Both selenious and Fi ^^T 
selenic acids form salts with the alkalies 
and bases, every way similar to the sulphites and sulphates, 
Selenid of sulphur is found native among volcanic products. 


Equivalent, 64. Symbol, Te. 

328. This rare substance is related to selenium and sul- 
phur. It forms compounds with gold and bismuth, found 
native as minerals. Pure tellurium is a tin-white, brittle 
substance, with a metallic lustre, and density of 6*26. It 
melts at low redness, and takes fire in the air, forming tel- 
lurous acid, TeO a . With hydrogen it forms a compound, 
analogous to arseniuretted hydrogen, and sulphuretted 



Equivalent, 14. Symbol, N. Density, *972. 

329. Preparation and History. — This gas forms four- 
fifths of the air, and is an essential constituent of most 
organic substances. It was first described by Rutherford, in 
1772. It is only mingled mechanically with oxygen in our 
atmosphere, which is not a chemical compound. 

It is most easily procured for purposes of experiment 
from the atmosphere, by withdrawing the oxygen of the air 

327. What of selenious acid ? 328. What of tellurium ? 329. Give the 
history of nitrogen. 





by phosphorus. This is easily 
done by burning some phos- 
phorus in a floating capsule, 
under an air-jar, upon the pneu- 
matic cistern, (fig. 248.) The 
strong affinity of phosphorus foi 
oxygen enables it to withdraw 
every trace of this element, 
leaving behind nitrogen nearly 
pure, containing about 7 ^th of 
phosphorus. The water soon ab- 
Fig. 248. g^jjg tne sn ow-white phosphoric 

acid. The first combustion of the phosphorus expels a 
portion of the air by expansion ; but as the combustion pro- 
ceeds, the water rises in the jar, until it occupies about 
•Jth of its space. When this experiment is performed over 
mercury, the white phosphoric acid remains unchanged. 
Nitrogen may be procured pure by passing a current of air 
over copper turnings in a tube of hard glass heated to 
redness : the oxygen is all retained by the copper, while 
nitrogen is given off. Nitrogen can also be obtained, by 
decomposing strong water of ammonia, by chlorine gas : 
the ammonia yields its hydrogen to the chlorine, and the 
nitrogen is given off. The apparatus (fig. 249) may be 

used for this 
purpose, in 

which p is 
an evolution- 
flask for chlo- 
rine, and the 
strong am- 
monia water 
is in to. Great 
care should 
be taken to 
prevent all 
the ammonia 
becoming sa- 
turated, as in 
Fig. 249. that case a 

How prepared ? How from ammonia ? What precaution is note i ? 
U'bat is the reaction ? 



IOTB0GEN. 201 

rerj dangerous compound (chloride of nitrogen) will be 
formed by the action of the chlorine, on the chlorid of am- 
monia produced in the process. The nitrogen collects in n. 
3C1+NH 3 =8HCL+N. 

830. The properties of nitrogen are mostly negative. It 
is a colorless/ tasteless, odorless, permanent gas. It has not 
been liquefied. It combines directly with no element, but 
indirectly it enters into most powerful combinations. In the 
atmosphere it appears to act chiefly as a diluent of oxygen. 
Its density is 0*972, or a little less than air. A 
taper immersed in it (fig. 250) is extinguished im- 
mediately. An animal placed in nitrogen dies from 
want of oxygen, and not because of any poisonous 
character in the gas, as might be inferred from its 
abundance in our atmosphere. Hence its name 
azote, from a privative, and the Greek zoe, life, to 
deprive of life. Nitrogen is derived from Latin 
nitrium, nitre, and gennao, I form. One hundred s ' 
volumes of water dissolve about two and a half volumes of 

The Atmosphere. 

331. The mechanical properties of the atmosphere have 
already been considered, (20.) The number and propor- 
tion of the constituents of the atmosphere are constant, 
although their union is only mechanical. Repeated analyses 
have shown that atmospheric air is always formed of nitro- 
gen, oxygen, watery vapor, a little carbonic acid, traces 
of carburetted hydrogen, and a small quantity of ammo- 
nia. The air on Mount Blanc, or that taken in a bal- 
loon by Gay-Lussac from 21,735 feet above the earth, 
had the same chemical composition as that on the surface, 
or at the bottom of the deepest mines. The carbonic acid, 
being liable to changes in quantity from local causes, is 
found to vary slightly. 

To the constituents already named, we may add the aroma 
of flowers and other volatile odors, and those unknown, 
mysterious agencies, which affect health, and are called mias- 
mata. From the results of numerous analyses, we state the 
composition of the atmosphere in 100 parts, to be — 

330. What its properties? What its function in air? How affects 
life? Hence, what name has it? Define the word nitrogen. 33L. 
What of air ? How are its constitnents ? What of its purity ? What 
arc its constituents ? 





Byiretght By 

Nitrogen 76-90 79-10 

Oxygen 23-10 20-90 



To this we must add from 3 to 5 measures of carbonic 
acid in 10,000 of air, about the same quantity of carburetted 
hydrogen, a variable quantity of aqueous vapor, and a trace 
of ammonia. Nitric acid is also sometimes found in small 
quantity in rain-water, formed in the air by the electrical 
discharges of thunder-clouds, and washed out by the rains. 
100 cubic inches of dry air weigh 31*011 grains. In 10,000 
volumes the constitution of the air will be, therefore — 

Nitrogen 7901 

Oxygen 2091 

Carbonic acid 4 

Carburetted hydrogen 4 

Ammonia trace 


332. The analysis of air is accomplished by any sub- 
stance which will remove the oxygen. But the accurate 
performance of this process requires numerous minute pre- 
cautions, any notice of which is out of place here. Eu~ 
diometry is the term applied to the common method of 
analysis for air. This term is derived from Greek words 
signifying a good condition of the air, and was employed 
because it was formerly thought that an analysis of the air 
would show if it was in a salutary 
condition. One of the simplest 
means of analyzing the atmosphere, 
consists in removing the oxygen 
by the slow combustion of phos- 
phorus. For this purpose a stick of 
phosphorus is sustained on a plati- 
num wire (fig. 251) in a confined por- 
tion of air, contained in a graduated 
glass tube, whose open end is be- 
neath water. A gradual absorption 
takes place, and in about twenty- 
four hours the water ceases to rise 
in the tube, by which we know that 
Fig. 251. the phosphorus has removed all Fi *' 25L 

Give analyses of air ? What is its composition in 10,000 volume* T 
*32. How analyzed ? What is eudiometry ? 




the oxygen. The water absorbs the resulting phosphorous 
acid, and we may read off, by the graduation on the tube, 
the amount of oxygen removed. A narrow-necked bolt-head 
shows this result in a more striking manner in the class-room, 
the large volume of air in the ball causing a very apprecia- 
ble rise of water in the stem during the course of a lecture, 
(fig. 252.) When speaking of hydrogen, we will mention 
another method of eudiometry. The agency of the air in 
combustion and respiration will also be explained under 
the appropriate heads. The air dissolved in water, and 
on which water-breathing animals live, is found to be 
decidedly more rich in oxygen than the atmospheric air. 
This is owing to the fact that oxygen is much more abun- 
dantly absorbed by water than nitrogen, in the proportion 
of -046 to *025. These numbers express, respectively, the 
ratio of solubility of the two gases in water. The air in 
water has the constitution — 

By analysis. By theory. 

Oxygen 32 31'5 

Nitrogen 68 68*5 

100 100-0 

Compounds of Oxygen and Nitrogen, 

333. Nitrogen unites with oxygen, forming five com- 
pounds, three of which are acids. Their names and consti- 
tution are thus expressed : — 


Protoxyd of nitrogen (nitrous oxyd) ; NO 

Deutoxyd of nitrogen (nitric oxyd) NO* 

Nitrous acid. NO t 

Hyponitric acid N0 4 

Nitric acid NO t 

As nitric acid is the source whence all the other com- 
pounds of nitrogen are obtained, we will commence with 
the history of that compound : — 

This important compound was known in the earliest days 
of alchemy, but it was Cavendish who, in 1785, first made 
known its constitution. He formed it by direct union of its 
elements over a solution of potash, by aid of a series of 
electrical sparks continually passed through a mixture 
of the two gases N and O, for several successive days, 

What of air dissolved in water ? 333. What are the oxygen com. 
pounds of nitrogen? Give the series. What is the source of other ni- 
trogen compounds ? 





in a close tube, (fie 258 ) 
The ends of the tube, con- 
taining the gases and pot 
ash solution, dipped into 
and contained mercury as 
a conducting medium for 
the electricity. Nitre was, 
Fig. 253. subsequently, found in the 

solution, thus giving the strongest evidence of a union of 
the two gases. 

334. Nitric Acid, "Aqua Fortis," N0 5 H0.— This power- 
ful acid is obtained by heating saltpetre (nitrate of potassa) 
or nitrate of soda with strong sulphuric acid. The nitric 
acid is displaced by the sulphuric, and distils over, being 
much more volatile than the sulphuric acid. 

335. The arrangement 
of apparatus required is 
seen in figure 254. The 
retort R contains the 
nitre in small crystals, 
and should be supported 
in a sand-bath ; or, if the 
quantity of nitre does not 
exceed a pound or two, a 
naked fire answers very 
well. An equal weight 
of 8ulphurie acid is then 
added, with care not to 
soil the interior neck of 
Ij: \f^ * ne retor k Heat is gradu* 

^ — -Jr ally applied, and the re- 
Fig. 254. ceiver kept cold by a con- 
stant stream of water distributed over its surface by a 
piece of filtering paper. No corks or luting of any kind 
can be used about the apparatus, as the vapors of concen- 
trated nitric acid attack all organic substances with energy, 
as also the alumina and other bases of clay-lute. In the 
first moments of the operation the vessels are filled with 
deep-red vapors of hyponitrous acid, due to the decomposi- 
tion of the first formed portions of nitric acid by the great 

334. What is the history of NO,? What was the experiment of Ca- 
? endish ? What is the process, fig. 254 ? What precautions are given f 




excess of sulphuric acid. As the distillation proceeds, 
the vessels become colorless and the distillate very nearly 
so. The red vapors appear again at the close of the opera- 
tion, and furnish a signal when to arrest the process and 
change the recipient. This is because the temperature rises 
toward the close, to the decomposing point of nitric acid. 
The bisulphate of potash in the retort remains some time 
after the heat is withdrawn in a state of quiet fusion, having 
a temperature of about 600°. When reduced to about 250°, 
hot water may be added in small portions at a time, and 
with care the retort may be saved, although it is often 
sacrificed from the crystallization of the sulphate of potassa. 
In the arts this process is conducted in large vessels of iron 
set in brick furnaces. 

336. Properties. — Nitric acid is a mobile fluid, nearly 
colorless, fuming, intensely acid, staining the skin instantly 
yellow, and acting with great energy on most metals and 
organic substances. It has usually a reddish color, due to 
the presence of hyponitric acid. When most concentrated 
it has a density of 1*51-1*52, and contains 86 parts in 
100, real acid. It boils at 187°. It is decomposed by 
light, evolving red fumes of hyponitric acid and free oxygen, 
which sometimes forcibly expels the stopper. It should, 
therefore, be kept in a dark place, or in black bottles. 
Poured on pulverized charcoal which has recently been 
ignited, it deflagrates it with energy ; warm oil of turpentine 
is immediately fired by it; and its action on phosphorus is 
too violent to be a safe experiment, without great precau- 
tion. The concentrated acid freezes at — 40° • but if 
diluted with half its weight of water, it freezes at about 1 J°. 
The green hydrous acid (343) freezes to a bluish-white solid. 
The dilute acid yields by distillation a product, at first more 
concentrated, but when it has a boiling point of 250° 
the product is of uniform strength, and contains 40 parts 
real acid in 100. Like sulphuric acid, it forms several 
definite hydrates, of which the highest is the strong acid 
described above. Anhydrous nitric acid N0 5 has been lately 
obtained by decomposing dry nitrate of silver by perfectly 
dry chlorine. Anhydrous ntrio acid crystallizes in colorless 
rhombs, which fuse at 30°; and it boils at 50° with decom- 

336. What are the properties of NO,? How doeiit aet on oombustt- 
blea? What of its hydrates? Of anhydrous NO,? 





position. It is soluble in water, evolving much heat, and 
yielding colorless, hydrous nitric acid 

337. Nitric acid is a powerful solvent of the metals, and 
carries them to their highest state of oxydation. This 
action is always attended with the production of binoxyd of 
nitrogen NO a and hyponitric acid. The nitrates are aU 
soluble in water. When fused with carbon they are de- 
composed with brilliant deflagration of the charcoal. Nitrfo 
acid decoloriies a solution of sulphate of indigo, and with a 
few drops of chlorohydric acid it dissolves gold-leaf. 

Passed in vapor through a poroelain tube heated white- 
hot it is decomposed, yielding nitrogen and oxygen. 

338. Protoxyd of Nitrogen NO, Nitron* Oxyd, or Laugh- 
ing Gas. — This gaseous compound of nitrogen is prepared 
by heating nitrate of ammonia NH 4 0.N0 5 in a glass flask, 

(fig. 255,) by the aid of a spiritjamp. 
The gas is given off at about 400° to 
500°, and is delivered by the bent tube 
to an air-jar on the pneumatic trough. 
The uitrate of ammonia, which is a 
crystalline white salt formed by neu- 
tralizing dilute nitric acid by carbonate 
of ammonia, is so constituted as to be 
resolved by heat alone into nitrous 
oxyd and water; thus, NH 4 0.N0 5 
become by heat 4HO + 2NO Con- 
sequently, the equivalents of these ele- 
ments show us, that 80 grains of nitrate 
I of ammonia, will yield 44 grains of 
Fig. 255. nitrous oxyd, and 36 grains of water. 

Care must be taken not to heat this salt too highly, as it then 
yields nitric oxyd and hyponitric acid. If a red cloud is seen 
during any part of the operation, the heat must be abated. 

339. Properties. — Protoxyd of nitrogen is a colorless gas, 
with a faint, agreeable odor, and a sweetish taste. With a 
pressure of fifty atmospheres at 45° F. it becomes a clear 
liquid, and at about 150° degrees below zero freezes into a 
beautiful clear crystalline solid. By the evaporation of this 
solid, a degree of cold may be produced far below that of 
the carbonic acid bath (151) in vacuo, (or lower than — 174° 

337. How does it affect metals ? What of nitrates ? 338. How is NO 
prepared ? Give the reaction ? What precaution is noted ? 339. What 
dire its properties ? What of its liquid ? What temperature ? 




F.) It evaporates slowly, and does not freeze, like carbonic 
acid, by its own evaporation. The specific gravity of 
nitrous oxyd is 1*527; 100 cubic inches of it weigh 47-29 
grains. Cold water absorbs about its own volume of this 
gas. It cannot, therefore, be long kept over water, but may 
be collected over the water-trough in vessels filled with warm 
water. It supports the combustion of a candle, 
(fig. 256,) and sometimes relights its red wick with 
almost the same promptness as pure oxygen. 
Phosphorus burns in it with great splendor. 
With an equal bulk of hydrogen, it forms a mix- 
ture that explodes with violence by the electric 
spark or a match : the residue is pure nitrogen, 
the oxygen forming water with the hydrogen. 
Passed through a red-hot porcelain tube it is re- Flg * 256 ' 
solved into its constituent gases. One volume of protoxyd 
of nitrogen contains 

1 volume of nitrogen 0*972 

£ volume of oxygen 0*552 

Theoretical density 1*524 

340. It may be breathed without injury, but it produces 
a remarkable excitement in the system, amounting to in- 
toxication, and, if carried far, even to insensibility. To pro- 
duce these effects without injury, it should be quite pure, 
and especially free from chlorine, and inhaled through a 
wide tube, from a gas-holder or bag. The presence of chlorid 
of ammonium in the nitrate employed should be especially 
avoided, as producing chlorine. There is a sweetish taste, and 
a sensation of giddiness, followed by joyous or boisterous 
exhilaration. This is shown by a disposition to laughter, a 
flow of vivid ideas and poetic imagery, and often by a strong 
disposition to muscular exertion. These sensations are 
usually quite transient, and pass away without any resulting 
languor or depression. In a few cases, dangerous conse- 
quences have followed its use, and it should always be em- 
ployed with great caution. In at least one case, in the labo- 
ratory of Yale College, it produced a joyous exhilaration of 
spirits, which continued for months, and permanent restora- 
tion of health. Its effects, however, on different individuals, 
are various. 

How does it act on combustibles? What is its volume ? 340. What 
its effect if breathed? 





Fig. 257. 

841 Deutoxyd or Binoxyd of Nitrogen, Nitric OxytL— 
This gas is easily prepared by adding strong nitric acid to 
clippings of sheet-copper, contained in 
a Dottle arranged with two tubes, (fig. 
257.) A little water is first put with the 
copper cuttings, and the nitric acid 
poured in at the tall funnel-tube until 
brisk effervescence comes on. In this 
case the copper is oxydized by a part of 
the oxygen of the acid, and the oxyd thus 
formed is dissolved by another portion of 
acid. The nitrogen, in union with the 
two equivalents of oxygen, is given off 
as nitric oxyd, which, not being ab- 
sorbed by water, may be collected over 
the pneumatic-trough. Many other 
metals have the same action with nitric acid. The action 
is renewed by continued additions of nitric acid. It is 
also obtained very pure by heating nitrate of potash 
K0.N0 5 with a solution of protochlorid of iron FeCl, in 
an excess of chlorohydric acid. 

342. Properties. — Nitric oxyd is a transparent, colorless 
gas, tasteless and inodorous, but excites a violent spasm in 
the throat when an attempt is made to breathe it. It has 
never been condensed into a liquid. Its specific gravity is 
1*039, and 100 cubic inches weigh 32*22 grains. It con- 
tains equal measures of oxygen and nitrogen uncondensed. 

A lighted taper is usually extinguished when immersed 
in it, but phosphorus previously well inflamed will burn in 
it with great splendor. When this gas comes into contact 
with the air, deep-red fumes are produced, by its union with 
the oxygen of the air to form hyponitric acid. If to a tall 
jar, nearly filled with nitric oxyd, standing over the well 
of the cistern, pure oxygen gas be turned up, deep blood- 
red fumes instantly fill the vessel, much heat is generated, 
and a rapid absorption results from the solution of the red 
nitrous acid vapors in the water of the cistern. 

343. Nitric oxyd is rapidly absorbed by solution of green 
sulphate of iron, forming a deep-brown solution of sulphate 
of peroxyd of iron. Colorless nitric acid also absorbs nitric 

341. What of NO,? How evolved? 342. Give its properties. Why 
irrespirable ? How affects combustibles ? In contact with air produces 
what? Give an illustration. 343. What absorbs it ? 





oxyd, and acquires first a yellow, then an orange-red, and 
finally a lively green color. This operation is best con- 
ducted in an apparatus of bottles arranged as in fig. 258, 
and called Woulf *s apparatus. The gas generated in a passes 

Fig. 258. 

in succession into the fluid of each vessel. The central tubes 
serve as safety-tubes. The colors named above are beauti- 
fully seen in the several bottles, the first becoming green 
before the last has gained an orange tint. By carefully 
heating the green acid, the hyponitric acid contained in it 
may be expelled. The deutoxyd of nitrogen decomposes 
the nitric acid, forming hyponitric acid, (345.) 

344. Nitrous Acid, N0 8 . — This is a thin, mobile liquid, 
formed from the mixture of four measures of deutoxyd of 
nitrogen with one measure of oxygen, both perfectly dry, 
and exposed after mixture to a temperature below zero of 
Fahrenheit. It has an orange-red vapor : the liquid at 
common temperatures is green, but at zero is colorless. 
Water decomposes it, forming nitric acid and deutoxyd of 
nitrogen. It forms salts, called nitrites. 

345. Hyponitric Acid, N0 4 . — When the green nitric 
acid obtained in the process just described (fig. 258) is 
cautiously distilled, hyponitric acid in notable quantity is 
collected in the refrigerated receiver. The apparatus is ar- 
ranged as in fig. 259. The green acid is heated in the retort 
r, by means of a water-bath w, over the lamp c, and the pro- 
duct is collected in the U tube t, placed in a refrigerant mix- 
ture. This acid is also procured by decomposing nitrate of 
lead in a porcelain retort by heat. Oxygen and hyponitric 

How does it affect NO, ? Explain the apparatus, fig. 257. 344. What 
of NO ? What are its salts ? 345. Hem is NO« obtained? 






acid are obtained, and the latter is collected as above. Tha 
is an orange-colored fluid, density 1-42, becoming red when 

Fig. 259. 

heated. It boils at 82°, and solidifies at 8°. Its vapor is 
intensely red, and has the density 1*73. This compound is 
hardly entitled to be considered as an acid, it does not form 
salts, but in contact with a base is decomposed, producing 
a nitrate and a nitrite. 


Equivalent, 32. Symbol, P. Density, 1-863. 

846. Bistory. — Phosphorus is an element nowhere seen 
free in nature, but it exists largely in the animal kingdom, 
combined with lime, forming bones, and is found also in 
other parts of the body. In the mineral kingdom it exists 
widely diffused in several well-known forms, particularly in 
the mineral called apatite, which is a phosphate of lime. 
It is introduced into the animal system by the plants used 
as food, whose ashes contain a notable quantity of phos- 
phate of lime. It was discovered in 1669, by Brandt, an 
alchemist of Hamburg, while engaged in seeking for the 
philosopher's stone, in human urine. Its name implies its 
most remarkable property, (phos, light, and phero, I carry.) 

S47. Preparation. — Phosphorus is procured in immense 

How as in fig. 258 ? What are its properties ? 346. Give the historj 
of phosphorus. Whence its name? 





if&antiiaes from burnt bones, for the manufacture of friction 
matches. The bones are calcined until they are quite 
white ; they are then ground to a fine powder, and fifteen 
parts of this are treated with thirty parts of water and ten 
of sulphuric acid : this mixture is allowed to stand a day or 
two, and is then filtered, to free it from the insoluble sul- 
phate of lime, formed by the action of the oil of vitriol on 
the bones. The clear liquid (which is a soluble salt of lime 
and phosphoric acid) is then evaporated to a syrup, and a 
quantity of powdered charcoal added. The whole is then 
completely dried in an iron vessel and gently ignited. After 
this, it is introduced into a stoneware or iron retort, to 
which a wide tube of copper is fitted, communicating with a 
bottle in which is a little water, that just covers the open 
end of the tube, (fig. 260 :) a small 
tube carries the gases given out to a 
chimney or vent. The retort being 
very gradually heated, the charcoal 
decomposes the phosphoric acid, car- 
bonic acid and carbonic oxyd gases are 
evolved, and free phosphorus flows 
down the tube into the bottle, where it 
is condensed. The operation is a criti- 
cal one. Splendid flashes of light are 
constantly given out during the ope- 
ration, from the escape of phosphu- 
retted hydrogen. The crude phos- 
phorus thus obtained is purified by 
melting under water, and it is then cast into glass tubes, 
forming the sticks in which it is sold. 

348. Properties. — Phosphorus is an almost colorless, semi- 
transparent solid, which at ordinary temperatures, cuts with 
the consistency and lustre of wax. At 32° it is brittle, 
and breaks with a crystalline fracture. Exposed to light, it 
soon becomes yellow and finally red. Its density by the 
late determinations, is 1 -826-1*840, and liquid 1-88. It is 
insoluble in water; but dissolves readily in bisulphuret of 
carbon ; in ether, alcohol, and various oils, it is partially 
soluble. It is obtained in fine dodecahedral crystals, from 
its solution in bisulphuret of carbon. It melts at 111° to 

Fig. 260. 

347. How prepared? How is the crude PO, decomposed? 348* 
What are its characters ? How crystallized ? How soluble ? 




ft limpid liquid : when fused beneath water, it is safely re- 
cast in small sticks, by drawing it into narrow glass tubes. 
It boils at 554°, forming a colorless vapor with the density 
4-226. Owing to its great inflammability, it is a very un* 
safe substance to handle, producing severe burns, very dif- 
ficult to heal. Any impurity, such as the presence of partly 
oxydized phosphorus, as from the nitrogen experiment, 
(fig. 248) renders it much more liable to inflammation. The 
heat of the hand, or the least friction, suffices to set fire to 
it. It must be kept under water, to which alcohol enough 
may be added to prevent its freezing in winter. If exposed 
to the air, it wastes slowly away, forming phosphorous acid. 
When in the dark, it is seen to be luminous. The vapor 
which comes from it has a strong garlic odor, which does 
not belong, either to the pure phosphorus, or its acid com- 
pounds. By this action the ozone of Schonbein is formed, 
(279.) A little defiant gas, the vapor of ether, or any 
essential oil, will entirely arrest the slow oxydation of phos- 
phorus in air. The presence of nitrogen or hydrogen seems 
to be essential to this operation, as, in pure oxygen, phos- 
phorus does not form phosphorous acid at common temper- 
atures. It burns in pure oxygen gas with great splendor, 
forming one of the most brilliant experiments in chemistry, 
(354.) Phosphorus is a violent poison. 

349. Red, or amorphous phosphorus, is a peculiar iso- 
meric modification of common phosphorus, produced by heat- 
ing it for a long time near its point of vaporization, in an 
atmosphere of hydrogen, or of carbonic acid. This effect 
takes place also when phosphorus is long exposed to the 
light : the exterior of the sticks becomes encrusted with a 
red powder, formerly supposed to be oxyd of phosphorus. 
Red phosphorus presents properties strikingly different from 
common phosphorus : the latter fuses, as we have seen, at 111° ; 
the former remains solid even at 482°, and at 500° returns 
to the condition of ordinary phosphorus. Red phosphorus 
can be preserved without change in air, has no sensible 
odor, and may even be heated to 392° without becoming 
luminous. Its specific gravity is 1-964. It does not com- 
bine with sulphur at the fusion point of that body, while 

What renders it more inflammable ? How is it kept ? If exposed to 
air, what happens ? How is its combustion in managed in fig. 264 1 
349. What is red phosphorus ? How produeed J Give its character* 
How is it recognized as the same bod/ ? 




common phosphorus unites with sulphur with a terrible ex- 
plosion. It is only from the identity of the compounds 
from these two modifications of phosphorus that it is shown 
that they are indeed one and the same body. The red 
phosphorus is preferred, from its greater safety, in the manu- 
facture of matches, and in medicine. 

Compounds of Phosphorus with Oxygen. 

350. The compounds of phosphorus with oxygm are 
four in number, namely : 

Oxyd of phosphorus P«0 

Hypophosphorous acid.... PO 

Phosphorous acid PO. 

Phosphoric acid POi 

351. Oxyd of phosphorus is formed when a stream of 
oxygen gas is allowed to flow from a tube __._ 
upon phosphorus, melted under warm water, 
as seen in fig. 261. The phosphorus burns 
under water and forms a brick-red powder, 
which is the oxyd in question, mingled with 
much unburnt phosphorus. The presence of 
oxyd of phosphorus with unburnt phosphorus 
renders the latter much more inflammable. 
The water over the oxyd of phosphorus in 
this experiment becomes a solution of phos- 
phorous and phosphoric acids. ^ 261# 

352* Hypophosphorous acid is a powerful deoxydizing 
agent, decomposiBg the oxyds of mercury and copper, and 
even sulphuric acid, with precipitation of sulphur and libe- 
ration of sulphurous acid : by these reactions it becomes 
exalted to phosphorus or phosphoric acid. It is prepared 
by decomposing the hypophosphite of baryta. 

353. Phosphorous acid P0 8 is formed by the slow com- 
bustion of phosphorus in the air : a stick of phosphorus ex- 
posed to air is immediately surrounded by a white cloud of 
this acid. Sticks of phosphorus, cast in small glass tubes, 
may be arranged as m fig. 262, in a funnel. Each stick is 
placed in a glass tube ah f slightly larger than itself, and drawn 
to a pointy 5g. 2ti3 ■ and these are arranged in a funnel and 

350. What are the compounds of P? 351. How is P«0 formed? 
S52. What of PO ? 353. How is PO. formed ? 





covered with an open bell, 
to keep out dust and- the 
fluctuations of air. The 
action then proceeds gra- 
dually, and a considerable 
quantity of the product 
is collected in the bottle 
beneath. When formed by 
combustion of phosphorus 
in a limited quantity of \Jj 
air, phosphorous acid is a _. OM 
Fig. 262. dry white powder. Con-** 263 * 

tact of humid air converts it into the above form, which 
always contains some phosphoric acid. It is one of the less 
powerful acids. By heat it decomposes the oxyds of mer- 
cury and silver. It forms salts called phosphites. 

354. Phosphoric Acid, P0 5 . — This acid is formed by the 
action of strong nitric acid on phosphorus, as well as from 
bones, by the action of sulphurip acid, as in the process for 
obtaining phosphorus, (347.) ^jjhen phosphorus is burned 
in a full supply of oxygen^gal^ this acid is the product. 
For this purpose, an arrangement like fig. 264 is adopted. 

Fig. 264. 
The large globe is filled by displacement with oxygen, 
dried by the chlorid of calcium vessel c. The phosphorus 
is burned in a capsule, supported at the bottom of the globe 
on a bed of dry gypsum, and is dropped in at pleasure by 
the porcelain tube t, whose orifice is closed by a cork. The 

Describe the arrangement, fig. 262. What are its properties 1 S64. 
How is PO a formed ? 




bottle with two necks receives the vapors of phosphoric acid, 
a draft being kept up by the porcelain tube p, which is 
made to act as a chimney, by the alcohol flame from the 
cup a. In this way the combustion is kept up at pleasure, 
as fresh oxygen is supplied by the hose p. In a dark room 
this experiment forms a most magnificent display of mellow 
light. Such is its avidity for water, that phosphoric acid 
hisses like a hot iron when added to it. It makes an intensely 
acid solution, which, evaporated to dryness and ignited, yields 
on cooling a transparent glassy solid, called glacial phos- 
phoric acid. 

355. Phosphoric acid forms three distinct hydrates with 
water, and three classes of salts. These salts give a beauti- 
ful example of the substitution of a metal for hydrogen in 
the production of salts. Let M represent a metal in the 
following formulae, and we have 

Actda, Salt*, 

Monobasic or metaphospboric acid HO.POf, giving metaphosphate MO.PO, 

Bibasic or pyrophosphorie acid ~~ 2HO.PO*, " pyrophosphate 2MO.PO> 

Tribaaic or common phosphoric acid.. SIlO.POi, " phosphate 3MO.PO* 

For a full account of these interesting modifications of 
phosphoric acid, the student is referred to Dr. Graham's 
excellent Elements of Chemistry. 

The compounds of phosphorus, especially the phosphates 
of lime and of magnesia, are very widely distributed in nature, 
and enjoy an important function in the economy of life. 
The tribasic phosphates produce with nitrate of silver a yel- 
low precipitate ; with solutions of magnesia and ammonia a 
fine granular one, (ammonio-phosphate of magnesia;) and 
the molybdate of ammonia detects the smallest trace of this 
acid even in the fluids of the body. 

356. Ghlorids of Phosphorus. — Of these there are two, 
the perchlorid PC1 S , and the terchlorid PC1 8 . The first 
is formed when phosphorus is introduced into a jar of dry 
chlorine. It inflames and lines the sides of the vessel 
with a white matter, which is the perchlorid of phosphorus. 
This compound is very unstable, and when put in water both 
it and the water suffer decomposition, and hydrochloric and 
phosphoric acids result. To form the other, PC1 8 , the appa- 
ratus used for the chlorid of sulphur may be employed, sub- 
stituting phosphorus for sulphur in the retort P, (fig. 245.) 

How from bones ? What are its properties ? What is glacial PO, t 
865. What of its hydrates ? What tests for PO, ? 356. What chloridt 
oC phosphorus are there ? How is PCI, formed ? 





The bromids, iodids, and sulphurets of phosphorus have 
the same constitution as the chlorids, and are formed by 
contact of the elements. They are unimportant, and the 
sulphuret is a very violent and dangerous compound to form* 



Equivalent 6. Symbol, C. Specific gravity in vapor, 0*829. 

857. History. — Carbon is an element found in all three 
kingdoms of nature. Charcoal and mineral coal, which are 
the two common forms of carbon, have been known from 
the remotest times of history. Its great importance in the 
daily wants of society makes it one of the most interesting 
of the elementary bodies, and our interest in it is not dimin- 
ished from the fact that the charcoal and mineral coal which 
we use as fuel and the black-lead of our pencils are, essen- 
tially, the same thing with that rare and costly gem, the 
diamond. The three distinct and very dissimilar forms of 
existence which this element assumes, give us one of the 
best examples known of the allotropism of bodies. We will 
very briefly mention the principal characters of the three 
forms of carbon: 1. The diamond; 2. Graphite or plum- 
bago; 3. Mineral coal and charcoal. 

358. The diamond is pure carbon crystallized. It takes 
the forms of the regular system, or first crystalline class, 
-(44,) of which the annexed figures are some of the common 
modifications. Its crystalline faces are often curved, as in 
fig. 266. The diamond is the hardest of all known sub- 
stances, and can be scratched or cut only by its own dust. 

Pig. 265. Fig. 260. Fig. 267. Fig. 268. Fig. 269. 

The solid angles of this mineral, formed by the union of curved 
planes, are much used, when properly set, for cutting glass, 

What of the bromids and sulphurate ? 357. Give the history of carbon. 
What is its equivalent? What of its allotropism? 358. What of the 
diamond ? 



CARBON. 217 

-which it does with great ease and precision. It has a specific 
gravity of 352, and the highest value of any kind of treasure. 
The most esteemed diamonds are colorless, and of an inde- 
scribable brilliancy, described as the " adamantine lustre." 
They are often slightly colored, of a yellowish, rose, blue, 
or green, and even black tint. The largest known dia- 
mond formerly belonged to the Great Mogul, and when 
found weighed 2769-3 grains, or nearly six ounces : it had 
the form of half a hen's-egg. The Pitt,or Regent diamond, 
was sold to the Duke of Orleans for £130,000. It weighs 
less than an ounce. This was the gem which Napoleon 
mounted in the hilt of his sword of state. The Koh-i-noor, 
or mountain of light, (the Great Mogul diamond,) which 
now belongs to Queen Victoria, was valued to the British 
government at two million pounds sterling, but its com- 
mercial value is about three millions of dollars, or £622,000. 
It weighed before its recent cutting, 1108 grains, or 277 
carats. This gem was found at Golconda. The diamond is 
usually found in the loose sands of rivers, and is gene- 
rally accompanied by gold and platinum. Its native rock 
is supposed to be a peculiar flexible kind of sandstone, 
called itacolumite; and it is sometimes found loosely 
imbedded in a ferruginous conglomerate in Brazil. A few 
diamonds have been found in the United States; chiefly 
in North Carolina. 

359. From its high refractive power the diamond is sup 
posed to be of vegetable origin. The sun's light seems to be 
absorbed by the diamond, since it phosphoresces beautifully 
for some time in a dark place, after it has been exposed to 
the sun. It is a non-conductor of heat and electricity, and 
is very unalterable by chemical means. It is infusible, 
and not attacked by acids or alkalies. But heated to redness 
in the air, it is totally consumed, and the sole product of its 
combustion is carbonic acid gas. 

360. (2.) Graphite or Plumbago. — This form of carbon 
is sometimes improperly called " black-lead" but it does not 
contain a trace of lead in its composition, and bears no re- 
semblance to it, except that both have been used to mark 
upon paper. 

This peculiar mine/al is found in the most ancient rocks, 

Give its form and characters. What is its lustre ? What are some of the 
highly valued diamonds ? What of Koh-i-noor ? Where is the diamond 
found? 859. What of its supposed origin? 360. What is plumbago? 




as well as with those of a more modern era. It is also fire* 
quently found in company with coal, and is sometimes formed 
artificially, as in the fusion of cast-iron. It almost always 
contains a trace, and sometimes several per cent, of iron, 
which is, however, foreign to it; otherwise it is pore carbon. 
It is very much used for making pencils, and the coarser 
sorts are manufactured into very useful and refractory melt- 
ing pots. The most valued plumbago for the finest drawing 
pencils has been brought chiefly from the Borrowdale mine, 
in Cumberland, England; but it is a common mineral in 
this country, as, for instance, at Stur bridge in Massachusetts, 
St. John in New Brunswick, and many other places. It is 
found crystallized in flat, six-sided prisms, a form altogether 
incompatible with that of the diamond. It is soft, flexible, 
and easily cut; its density is 2*20; feels greasy, and marks 
paper. It is quite incombustible by all ordinary means, but 
burns in oxygen gas, forming only carbonic acid gas, and 
leaving a red ash of oxyd of iron. 

361. (3.) Coal. — The vast beds of mineral carbon, known 
as anthracite, bituminous coal, brown coal, and lignite, are 
all of them nearly pure carbon. Of the first two of these, 
no country has such abundant and excellent supplies as the 
United States. These accumulations of fuel are the remains 
of the ancient vegetation of the planet, which, long anterior 
to the creation of man, a bountiful Providence laid away in the 
bowels of the earth for his future use. Bituminous coal differs 
from anthracite only in having a quantity of volatile hydro* 
carbon united with it, which is wanting in the anthracite. 
This opake combustible mineral is entirely a non-conductor of 
electricity, and some of its varieties excite resinous electricity. 

362. Charcoal from wood is the carbonized skeleton of 
the woody fibre which is found in all plants. The best 
charcoal is made by heating sticks of wood in tight iron 
vessels, without contact of air, until all gases and vapors 
cease to be given off. A great quantity of acetic acid, tar, 
and oily matters, with water, are given out, and a jetty 
black, brittle, hard charcoal is left behind, which is a per- 
fect copy of the form of the original wood. It is a non-con- 
ductor of heat, but conducts electricity almost as well as a 
metal. It is a very unchangeable substance, insoluble in 

Where found? What its character? 361. What of coal? What its 
origin ? What difference between anthracite and bituminous ? What of 
It* electrical character? 362. What is charcoal ? What its characters? 



CARBON. 219 

water, acids, or alkalies, suffers little change from long ex- 
posure to air and moisture, and does not yield to the most 
intense heat to which it can be subjected, if air is excluded. 

363. Charcoal has the property of absorbing gases to a 
most remarkable degree, at common temperatures. A frag- 
ment of recently heated charcoal, of a convenient size to be 
introduced under a small air-jar over the mercurial cistern, 
will soon take up many times its own volume of air, as will 
appear by the rise of the mercury in the air-jar. In this 
case it absorbs more oxygen than nitrogen, the residual air 
having only eight per cent, of oxygen in it. On heating, 
it again parts with the gas it has absorbed. The power of 
absorption seems to depend entirely on the natural elasticity 
of the gas, and not at all on its affinity for carbon. Those 
gases that are most easily reduced to a fluid condition by 
cold and pressure, are most abundantly absorbed by char- 
coal. Charcoal from hard wood with fine pores has this 
property in the highest degree. Thus, charcoal from box- 
wood freshly prepared, will absorb of ammoniacal gas 90 
times its own volume ; of muriatic-acid gas, 85 times ; of 
sulphuretted hydrogen, 81 times ; of nitrous oxyd, 40 times; 
of carbonic acid, 32 times ; of oxygen, 9-25 times; of nitro- 
gen, 1*5 times; and of hydrogen, 1*75 times its own 

364. Charcoal also has the power of absorbing the bad 
odors and coloring principles of most animal and vegetable 
substances. Tainted meat is made sweet by burying it in 
powdered charcoal, and foul water is purified by being 
strained through it The highly colored sugar-syrups are 
completely decolorized by being passed through sacks of 
animal charcoal, (bone-black,) prepared by igniting bones. 
It also precipitates bitter principles, resins, and astringent 
substances from solution. Common ale or porter becomes 
not only colorless, but also in a good degree deprived of its 
bitter principles, by being heated with and filtered through 
animal charcoal. This property is lost by use, and regained 
by heating it afresh. Its power of absorption seems similar 
to that possessed by spongy platinum, (251.) Hydrogen, 
in small quantity, is very obstinately retained in the pores 
of charcoal, and water is consequently always produced from 

363. What of its absorbing power? What regulates its power with 
irions gases ? 364. What of its disinfecting and decolorising powers ? 

Digitized by VjOOQiC 



the combustion of carbon in pure oxygen gas. Carbon bat 
a greater affinity for oxygen at high temperatures than any 
other known substance, and for this reason it is useful in 
reducing the oxyds of iron and other oxyds to the metallic 
state. Lamp-black is a pulverulent variety of carbon, pro- 
duced from the imperfect combustion of oils and resins. 

Compounds of Carbon with Oxygen. 

365. The compounds of carbon, oxygen, and hydrogen 
embrace a majority of the bodies described in the organic 
chemistry ; which is therefore not improperly termed the 
chemistry of the carbon series. We will consider at pre- 
sent, however, only carbonic acid and carbonic oxyd. 

366. Carbonic Acid, CO a . — History, — This is the sole 
product of the combustion of the diamond or any pure carbon 
m the air, or in oxygen gas. It was first recognized and 
described by- Dr. Black, in 1757, under the name of fixed 
air. This philosopher proved that limestone and magne- 
sian rocks contained a large quantity of this gas in a state 
of solid combination with the earths, and also that it was 
freely given out in the processes of fermentation, respira- 
tion, and combustion. 

367. Preparation. — Carbonic acid is easily procured by 

treating any car- 
bonate with a di- 
lute acid. Car- 
bonate of lime, in 
the form of mar- 
ble powder, is 
usually employed 
for this purpose: it 
is put with a little 
water into a two- 
mouthed bottle A, 
(fig. 270;) dilute 
chlorohydric acid 
is turned in at the 
tube-funnel b f 
when the gas is 

Fig. 270. 

What is lamp-black? 365. What of the compounds of C with 
hydrogen, Ac.? 366. What is CO,? What was Black's discovery? 
t67. How is CO a prepared ? 



CARBON. 221 

sot free with effervescence, and escapes through the bent tube 
at a. Its weight enables us to collect it in dry bottles, by 
displacement of air, as in the case of chlorine. It may 
also be collected over water. No heat is required, and 
the acid is added in small successive portions, the gas being 
freely evolved at each addition. When obtained by the 
action of monohydrated nitric acid on bicarbonate of am* 
monia, the carbonic acid evolved retains a cloudy appear- 
ance, even after passing through water, which renders it 
visible — a point of some importance in experiments with 
this gas. 

36o. Prapertie*. — At the common temperature and pres- 
sure, carbonic acid is a colorless, transparent gas, with a 
pungent and rather pleasant taste and odor. At a tem- 
perature of 32°, and a pressure of 30 to 36 atmospheres, it is 
Condensed into a clear limpid liquid, not as heavy as water, 
which freezes by its own evaporation into a white, snow-like 
substance. Wc have already described (151) the apparatus 
and process by which this interesting experiment is per- 
formed. Carbonic acid is about once and a half as heavy 
as common air, having a specific gravity of 1-529 ; and 100 
cubic inches therefore weigh 47*26 grains. Owing to its 
weight, it may be poured from one 
( vessel to another, (fig. 271.) Car- 
bonic acid instantly extinguishes 
a burning taper lowered into it, 
even when mingled with twice 
or three times its bulk of air. 
Burning sulphur and phosphorus 
are also immediately extinguished 
in this gas. Potassium, however, 
quite clean, may be burned in a 
Florence flask filled with dried 
carbonic acid; the potassium is 
ignited by application of heat, and 
Fig. 271. t ne carbon is then deposited on 

Che glass vessel. Fresh lime-water agitated with this gas, 
rapidly absorbs it, becoming at the same time milky, from 
the production of the insoluble carbonate of lime; soluble, 
however, in excess of carbonic acid. In this way the pre- 

868. What its properties ? What its density ? How does it affect com- 
bustion ? How is it decomposed ? 




sence of carbonic icid in the atmosphere is easily detected, 
and this gas is distinguished from nitrogen by the same 

369. Cold water recently boiled absorbs rather more than 
its own volume of carbonic acid gas, but with pressure 
more will be taken up, in quantity exactly proportioned 
to the pressure exerted. The solution has a pleasant acid 
taste, and temporarily reddens blue litmus paper. The 
"soda water/' so much used as a beverage, is usually only 
water strongly impregnated with carbonic acid, the soda 
being generally omitted in its preparation. The efferves- 
cence of this, as well as of small beer and sparkling wines, 
is due to the escape of this gas. Natural waters have 
usually more or less of this gas dissolved in them; and some 
mineral springs, like the Saratoga and Ballston springs, 
and the Seltzer water, are highly oharged with carbonic 

370. Death follows the inspiration of carbonic acid, 
even when largely diluted with air. It kills by a specific 
poisonous influence on the system, resembling some narco- 
tics, and is unlike nitrogen in this particular, which 
kills only by exclusion of air. Instances of death from 
sleeping in a close room where a charcoal fire is burning, and 
from descending into wells which contain carbonic acid, are 
lamentably frequent. The latter accident may be avoided 
by taking the obvious precaution to lower a burning candle 
into the well before going into it, when if the candle burns 
with undiminished flame, all may be considered safe, but 
its being extinguished is certain evidence that the well is 
unsafe. Wells containing carbonic acid may often be freed 
from it by lowering a pan of recently-heated charcoal into 
the well, which will soon absorb thirty-five times its bulk 
of this gas, (368,) thus removing the evil. Even so small 
a quantity of carbonic acid as 1 or 2 per cent, produces, after 
some time, grave effects on respiration. Small animals 
thrown into a vessel full of this gas, may be recovered by im- 
mersion in cold water. The so-called Black Hole of Calcutta 
is a noted instance of the fatal effects of respiring an atmo- 
sphere overcharged with carbonic acid. 

369. What of its solution in water? 370. What is its effect on life ! 
Where do accidents often happen ? How prevented ? What quantity 
is injurious ? 






371. Numerous natural sources evolve large quantities of 
carbonic acid, particularly in volcanic districts. The Grotto 
del Cane, in Italy, (dog's grotto,) is a well-known example 
of the natural occurrence of this gas. But the quantity 
evolved there is trifling compared to that, which escapes 
constantly from Lake Solfatara, near Tivoli, whose surface ia 
violently agitated with the gases boiling through it. 

It is always present in the air, being given off by the 
respiration of all animals; and, besides the other sources 
already named, is an invariable product of all common 
cases of combustion. 

All the carbon which plants secrete in the process of 
their development, is derived either from the carbonic acid 
of the atmosphere, which they decompose by the aid of 
sunlight and their green leaves, retaining the carbon and 
returning the pure oxygen to the air ; or it is absorbed by 
their rootlets, and then decomposed by the sun's light at the 
surface of the leaf. 

372. Carbonic acid is formed of equal volumes of its 
two constituent gases, condensed into one. For this rea- 
son the air suffers no change of bulk from the enormous 
quantities of this gas which are hourly formed and decom- 
posed on the earth. This acid unites with alkaline bases, 
forming an important class of salts, (the carbonates,) which 
are decomposed by even the vegetable acids, with the escape 
of carbonic acid. 

373. Carbonic Oxt/d, CO. — Preparation. — TMa * 
is most easily 
obtained from 
oxalic aoid. 
This acid, when 
treated with 
five or six times 
its volume of 
sulphuric acid, 
in the flask a, 
<;fig. 272), is 
yielding equal 
volumes of car- 

Fig. 272. 

3T1. What sources are named for it ? How in the air ? Whence the car- 
bon of plants ? 372. What is its constitution ? What are its salts called f 
373. How is CO prepared ? What of oxalic acid ? * 




bonio add and carbonic oxyd. Thus, C 9 8 +HO— C0 8 +C0, 
the water remaining with the sulphuric acid. The carbonio 
acid is easily removed by a solution of caustic potash in the 
wash-bottle o. Dry, finely-powdered, yellow prussiate of 
potash, when decomposed by ten times its weight of sulphuric 
acid, in a very capacious vessel, yields an abundant volume 
of pure oxyd of carbon. 

374. Properties. — This is a colorless, almost inodorous 
gas, burning with a beautiful pale-blue flame, such as is 
often seen on a freshly-fed anthracite fire. Its specific gravity 
is a little less than that of air, or -967 ; and 100 cubic 
inches of it weigh 30*20 grains. Water absorbs about ^ 9 
of its volume of it; it does not render lime-water milky, 
and explodes feebly with oxygon. It is not respirable, but 
is even more poisonous than carbonio acid, producing a 
state of the system resembling profound apoplexy. This 
gas is very largely produced in the process of reducing iron 
from its ores in the high furnace. 

Carbonic oxyd is formed of half a volume of oxygen, 
and one volume of carbon, or two volumes of carbon and 
one of oxygen, condensed into two volumes. 

375. Chloro-carbonic oxyd is formed of equal volumes of 
chlorine and oxyd of carbon. This union with chlorine is 
produced . by the influence of light, and hence the product 
was called phosgene gas. This is a pungent, highly odorous, 
suffocating body, possessing acid properties, and decomposed 
by water. Its formula is CO. CI, or carbonio acid in which 
chlorine occupies the place of an atom of oxygen. Its 
density is 3-407. 

Compounds of Carbon with the Chlorine Chroup. 

The chlorids of carbon will be described in the organic 

376. Bisulphuret of Carbon, C.S a . — This remarkable 
product is formed by the direct union of its elements. 
In a retort of fire-clay C, (fie. 273,) fragments of charcoal 
are placed. A porcelain tube b descends nearly to the 
bottom of the retort, being luted with clay at a. When 
the retort is red hot, small bits of roll sulphur are from 

374. What are the properties of CO? 375. What is chloro-carbonk 
oxyd ? 376. How is biiulphuret of carbon prepared in fig. 273 ? 

Digitized by VjOOQ IC 



Fig. 273. 

Fig. 274. 

time to time dropped in at b, and 
this orifice immediately closed by 
a cork. The vapor of sulphur rising 
among the ignited carbon combines 
with it, and bisulphuret of carbon 
distills, is con- 
densed by a 
and collected 
in the bottle 
surrounded by 
cold water, o. 
The first pro- 
duct is yellow, from free sulphur, and is 
purified by a seoond distillation. When 
pure, bisulphuret of carbon isacolorless, 
very mobile and volatile fluid, with a 
disgusting odor, altogether peculiar. Its 
density at 32° is 1-293 ; at 60°, 1-271. 
It boils at 110°, and its vapor has a 
density of 2-68. Its power of refracting light is very remark- 
able. It dissolves sulphur, phosphorus, and iodine, these bodies 
being deposited again in beautiful crystals by the evapora- 
tion of the sulphuret of carbon. G-utta percha and India* 
rubber are also soluble in it. It burns in the air at about 
600°, with a pale blue flame, producing carbonic and sul- 
phurous acids. It forms an explosive mixture with oxygen, 
and a combustible one with binoxyd of nitrogen. It dis- 
solves easily in alcohol and ether, and is precipitated again 
by water. 

Carbon with Nitrogen. 

377. Cyanogen, C 9 N or Cy. — This important and in- 
teresting compound of carbon and nitrogen belongs appro- 
priately to the organic chemistry ; but it deports itself so 
much like an elementary substance and its compound with 
hydrogen, (cyanhydric or prussic acid,) and its metallic 
compounds also, are of so much general interest, that it is 
proper to mention this compound-radical here. 

What are its properties? What its solvent powers? 877. What % of 
cyanogen ? Giye its formula. 





Carbon and nitrogen combine only indirectly. If car- 
bonate of potassa and carbon are heated together in a por- 
celain tube, while nitrogen is passing over them, oxyd of 
carbon escapes, and cyan id of potassium in considerable 
quantity remains in the tube, and may be dissolved out by 
water. Cyanogen is usually prepared in the laboratory, by 
decomposing cyanid of mercury (CyHg) in a small retort 
by heat, ana collecting the gas over mercury. It is more 
economically and abundantly prepared, however, by healing 
a mixture of 6 parts of dried ferrocyanid of potassium, and 
9 parts of bichlorid of mercury in a flask of hard glass. The 
cyanid of mercury formed is decomposed immediately into 
mercury and cyanogen. 

378. Properties. — Cyanogen is a colorless gas, of a strong 
and remarkable odor, resembling peach-pits. Its density 
'A 1*86. At a temperature of — 4°, it is liquefied, and at 
common temperatures, with a pressure of 4 or 5 atmo- 
spheres. Liquid cyanogen is a colorless, very mobile fluid, 
whose density is about 9. By keeping a short time, it 
undergoes a change, becomes brown, and deposits a brown 
powder in the glass. This is paracyanogen, an isomeric 
form of cyanogen, a portion of which is always seen as a 
residue in the retort after decomposing cyanid of mercury. 

Cyanogen burns with a magnificent and characteristic 
purple flame, giving carbonic acid and free nitrogen. For 
this purpose a large vessel may be filled with the gas, by 
displacement. Water dissolves 4 or 5 times its volume of 
cyanogen, and alcohol 24 or 25 times its volume. Cyanogen 
forms cyanids — compounds almost exactly analogous to the 
chlorids of the same metals, and in which cyanogen com- 
ports itself like an element. 

Cyanogen is formed from 1 volume of carbon vapor, weighing 0*8290 
and 1 volume of nitrogen " 0*9713 


which is a close approximation to 1-86, the result of ex- 

How do C and N unite ? How is Cy usually prepared ? How from 
bichlorid of mercury and ferrocyanid of potassium ? 378. What are its 
properties ? How liquefied ? How does the liquid change ? How does 
Cy burn ? What compounds does it form ? Analogous to what ? What 
is its volume composition ? 



silicon. 227 


Equivalent, 21*3. Symbol, Si. Density in vapor, (hypo* 
thetical,) 15 29. 

379. Silicon combined with oxygen, forming silica, is 
abundantly distributed throughout the earth. It is said to 
form ith part of the crust of the globe. 

Silicon is prepared by decomposing the double fluorid of 
silicon and potassium by metallic potas- 
sium. The potassium, in small pieces, 
is mingled with £th its weight of the 
dry white powder of .the double fluorid, 
in a test-tube, (fig. 275,) which is then 
heated. Reaction occurs as soon as 
the bottom of the tube is red, and 
spreads through the whole mass. The 
«ool residue is treated with water, 
which dissolves the fluorid of potas- lg * 

sium, and leaves silicon. Thus, 

3KF.2SiF 8 +6K = 9KF+2SL 

380. Properties. — Silicon is a nut-brown powder, and a 
non-conductor of electricity. Heated in air or oxygen it burns, 
forming silica. If heated in a close vessel, it shrinks, and 
becomes more dense. Before ignition it is soluble in hydro- 
fluoric acid, but after this it is insoluble, and is incombustible 
in the air or oxygen gas. It seems then to resemble the 
graphite variety of carbon. These two diverse conditions 
of silicon are probably connected with the two states in which 
silica occurs. 

381. Silicic acid, or silica, SiO s , is far the most import- 
ant of all the compounds of silicon. It exists abundantly 
in nature, in the form of rock crystal, agate, common un- 
crystallized quartz, silicious sand, &c. ; it also enters largely 
into combination with other substances to form the rock 
masses of the globe. It is a very hard substance, easily 
scratching glass, and is difficult to reduce to a powder ; its 
specific gravity is 2 -66. Its usual crystalline form (fig. 276) is 
a six-sided prism, with two similar pyramids. It is infusible 

379. What of silicon ? Give its equivalent. How is it prepared ? 6iv« 
the reaction. 380. What are its properties? What two States? 381. 
What is silica? 

Digitized by VjOOQ iC 




alone, except by the power of the compound blow* 
pipe. It dissolves with effervescence in fluohydrie 
acid and in fused carbonate of soda or potash. No 
acid, except the hydrofluoric, has any effect on silica. 
When in its finest state of division it is still harsh 
Fig/276, and gritty to the touch or between the teeth. 

382. When silica is fused in 4 or 6 times its weight of car- 
bonate of soda or potassa, and this mass is treated with a 
large volume of dilute chlorohydric acid until it manifests a 
decidedly acid reaction, the silica after some time separates 
as a transparent, tremulous jelly. This is soluble hydrated 
silica. If dried, it again becomes gritty and insoluble as 
before. Most natural waters contain some small portion of 
soluble silica; it has often been seen in this state in mines; 
and on breaking open silicious pebbles, the central parts are 
sometimes semifluid and gelatinous. The hot waters of the 
great geysers in Iceland, and of other hot springs, also dis- 
solve large quantities of silica, probably aided by alkaline 
matter. Agates, chalcedony, carnelian, onyx, and similar 
modifications of silica have been deposited from the soluble 
state. It is in this condition, no doubt, that silica enters 
the substance of many vegetables, as, for instance, the reeds 
and grasses, which have often a thick crust of silica on their 
bark. It is in this form also that silica acts as the agent of 

383. The acid powers of silica are seen only at high tem- 
peratures, when it saturates the most powerful alkalies and 
displaces other acids, forming silicates. Hence its great use in 
the art of glass-making, as it is the basis of all vitreous 
fabrics, including porcelain and potters 1 ware, which are all 
silicates. Soluble glass is formed when an excess of alkali 
is employed; and liquor of flints is an old term applied to a 
solution of silicate of potassa or soda. 

384. Chlorine, bromine, fluorine, and sulphur, all form 
compounds with silicon, having the formula 8iK a , or exactly 
the formula for silica. The chlorid of silicon is formed by 
passing dry chlorine over a mixture of fine silicious sand 
and charcoal in a porcelain tube heated to redness. It is a 
colorless, mobile liquid, having a density of 1-52, and boil- 
ing at 138°. It is decomposed by water into silica and 

What its forms in nature ? 382. When fused with alkali, how is it 
separated ? How does it exist in water and plants ? 383. What of its 
acid powers ? 384. What does S form with class II ? What of its chlorid f 





•hloroh ydri J acid. Bromid of silicon is formed in a similar 

385. Fluorid of Silicon, (flito-silicic acid,') may be pre- 
pared by heating sulphuric acid with fluor-spar in powder, to 
which is added twice its own weight of fine silica or powdered 
glass. The apparatus should be quite dry : 

Fluorspar. Silica. Sal. Acid. Sal. Lime. Water. Fluorid Silicon. 

8CaF + SiO, + 8(SO,.HO) = 3(CaO.SO t ) + 3HO + SiF,. 

Fluorid of silicon is a colorless gas, irrespirable, and de- 
composed by water. Its density is 3*57. It forms dense 
white vapors in contact with the moisture of the air. Passed 
into water it is immediately decomposed, gelatinous silica is 
precipitated, and the water becomes a solution of hydro-fluo- 
hi licic acid. The reaction is 

3SiF 8 +3HO=3HF.2SiF 8 +Si0 8 . 

The fluorid of silicon should not pass directly into the 
water from the gas tube, but 
into some mercury on which 
the water rests, as in fig. 
277. If this precaution be 
neglected the open end of 
the gas tube will become 
plugged with deposited sili- 
ca. The silica obtained in 
this operation, when well 
washed, is quite pure. The 
hydro-fluosilicic acid forms 
an insoluble salt with potas- 
sium 3KF.2SiF,. Fig. 277. 

Equivalent, 10-90. 


Symbol, B. Density in vapor, (hypo* 
thetical,) -751. 

386. Boron is known chiefly by its compounds, borax and 
boracic acid. Boracic acid is found in nature, either free 
or combined with various bases ; but it is rather a rare sub- 
stance. Boron is prepared by heating the double fluorid of 

385. What is its fluorid ? Give the reaction by which it is produced ? 
What its characters? How does water affect it? What is hydro-fluosili- 
eic acid ? Explain its production as in fig. 277. 386. What is boron ? 
How distributed in nature ? What its equivalent? 




boron and potassium in an iron vessel, with potassium, an 
in case of silicon. Boron is a dark olive-green powder. 
Heated to 600° in air it burns brilliantly, forming boracio 
acid. It does not conduct electricity, and is insoluble in 
water. Heated out of contact of air it suffers no change. 

387. Boracic Acid, BO s , is exhaled from volcanic vents, 
as in Vulcano, one of the Lipari Islands, and also more 
abundantly in the Tuscan maremma, not far from Leghorn. 
There it issues, accompanied by jets of steam, from the soil. 
These jets have been carried into lagoons of water constructed 
around them, where the boracic acid is taken up by the 
water. The heat of the earth affords the means of evapo- 
rating the water. Figure 278 shows one of these masonry 
basins, 0, built around the jets, Qsvffoni.) A series of 
these, four or five in number, are arranged one above the 
other: the least concentrated solutions occupy the upper 
basin, and are in turn, once in twenty-four hours, drawn off 
to- the lower, and finally to the evaporating pans E F, also 
heated by the escaping steam from the earth. In this man- 
ner the solution is brought to crystallize, and is purified by 
repeated crystallization. The production of boracic acid from 
this source equals two millions and a half pounds per year. 

Fig. 278. 

388. In the laboratory, boracic acid is obtained by de- 
composing borax of commerce. For this purpose, one part 
of borax is dissolved in two and a half parts of boiling water, 
and chlorohydric acid added until the liquid is strongly acid. 
On cooling, the boracic acid crystallizes in elegant tufts of 
scaly crystals, and is purified by a second crystallization. 
Boracic acid is a white pearly substance in thin scales : these 
have a feeling like spermaceti, are feebly acid to the taste, 
and soluble in twelve parts of boiling and in fifty parts of 

387. How is BO, found ? Describe the Tuscany lagoons. How are 
they heated? Whence the B0 3 ? 388. How is BO, prepared in the 
laboratory ? What are its properties ? 



HYDROGEN. % 281 

cold water. A boiling saturated solution deposits fths of its 
acid on cooling. The crystals contain 43 per cent, of water. 
By heat it fuses in its crystallization-water, which is finally 
expelled, and the acid, when heated to redness, fuses to a 
clear glass, which may be drawn out in fine threads. This 
glassy acid loses its transparency by keeping for some time. 
Boracic acid is a feeble acid in solution, but it expels sul- 
phuric acid from the sulphates at a red heat and forms glass 
with oxyds of lead and bismuth, of very high refractive 
powers. Alcohol dissolves boracic acid, and the solution, 
when set on fire, burns with a peculiar green flame, charac- 
teristic of boracic acid. Hydrous boracic acid is volatile by 
vapor of water, but the glassy acid is quite fixed at the 
highest temperatures. Boracic acid and the borates are 
much used as fluxes, to promote the fusion of other bodies. 

389. Cfdorid of Boron, BC1 8 , is formed in the same man- 
ner as chlorid of silicon. It is a colorless gas of a specific 
gravity of 4 09, decomposed by water into chlorohydric and 
boracic acids. 

390. Fluorid of Boron, BF 8 . — This gas is obtained when 
we heat together 2 parts of fluor-spar and 1 part of fused 
boracic acid in a vessel of porcelain at redness. 7BO.+ 
3CaF=3(Ca02B0 8 )+BF a . It is a colorless, suffocating 
gas, strongly acid, very soluble in water, and exceedingly 
greedy of it, so that it even carbonizes organic substances to 
obtain it, in the manner of sulphuric acid. Water dissolves 
700 or 800 times its volume of this gas. 

If fluor-spar, boracic acid, and concentrated sulphuric 
acid are heated together in a glass retort, a gas of a brownish 
color, very acid, and breaking on the. air in white fumes, is 
obtained : this is hydro-fluoboracic acid. It must be collected 
over mercury. 



Equivalent, 1. Symbol, H. Density, 0-0692. 

391. History. — Hydrogen was first described as a dis- 
tinct substance by the English chemist Cavendish, in 1766, 
and was called by him inflammable air. It had previously 

What dissolves it? What is characteristic of BO t ? How does heat 
affect it? 389. What of BC1. ? 390. What of fluorid of boron ? What 
of its properties ? 391. What is the history of hydrogen ? Its equivalent? 




been confounded with other combustible gases, several of 
which had been long known. Hydrogen exists abundantly 
in nature as a constituent of water, and also of nearly all 
animal and vegetable substances, in such proportions as to 
form water when these bodies are burned. It is named 
from the Greek httdor, water, and gennao, I form. 

892. Preparation. — This gas is generally prepared by 
the action of dilute sulphuric acid on zinc or iron. Zinc is 
usually preferred. The acid is diluted with four or five 
times its bulk of water, and the operation may be conducted 

Fig. 279. 

in a glass retort, or more conveniently by using a gas- 
bottle a, (fig. 279,) containing the zinc in small fragments, 
to which the dilute acid is turned through the tube-funnel 
b. The shorter tube /, with a flexible joint, conveys the 
gas to the air-jar standing in the cistern g. No heat is re- 
quired in this operation. An ounce ot 
zinc yields 615 cubic inches of hydro- 
gen gas. Zinc is readily granulated, 
by being turned, when melted, into 
cold water. When hydrogen is re- 
' quired in large quantity, a leaden pot 
or stone jar, properly fitted, and hold- 
ing a gallon or more, is used to contain 
the requisite charge of materials, and the gas is stored for 
use in a gas-holder, or India-rubber bag, (fig. 280,) (281.) 
393. The reaction in this case is between the zinc and 

Fig. 280. 

How does it exist ? 392. How is it prepared and stored ? 393. What 
Is the reaction ? 




Hie sulphuric acid, the hydrogen of the latter being replaced 
by the zinc, thus: SO,.HO+ Zn = S0 8 .ZnO+H. 
If ohlorohydric acid had been used, the reaction is still more 
simple, thus: HCl-f-Zn = ZnCl-f-H. . 

Water is essential to the rapidity of the action, by dissofv 
ing the sulphate of zinc, which is insoluble in strong sulphu- 
ric acid, and unless removed, immediately arrests the process. 

394. Hydrogen gas, 
when obtained from 
iron, has a peculiar and 
offensive odor, due to 
the presence of a vola- 
tile oil formed from 
the carbon always pre- 
sent in iron. That pro- 
cured from zinc is 
also somewhat impure. 
Traces of sulphuretted ' nrrr ^T 
hydrogen and carbonic 
acid are usually found in hydrogen, from impurity in the 
metals employed ; and also a trace of both iron and zinc is 
raised in vapor, and gives color to the flame of common 
hydrogen. Most of these impurities are removed by pass- 
ing the gas through a second bottle d, (fig. 281,) containing 
an alcoholic solution of caustic potash. Water only, in d, 
removes the vapor of acid found usually in the gas. 

395. Properties. — Hydrogen is a colorless, inflammable 
gas : it has never been liquefied. It refracts light very pow- 
erfully, and has the highest capacity for heat of any known 
gas. It is, when quite pure, inodorous and tasteless, and 
may be breathed without inconvenience when mingled with 
a large quantity of common air. The voice of a person who 
has breathed it acquires for a time a peculiar shrill squeak. 
It cannot, however, support respiration alone, and an animal 
plunged in it soon dies from want of oxygen. Water ab- 
sorbs only about one and a half per cent, of its bulk of pure 
hydrogen gas. Sounds are propagated in hydrogen with 
but little more power than in a vacuum. 

Hydrogen is the lightest of all known forms of matter, 

How is water necessary to it? 394. What renders it impure ? How 
Is it purified ? 395. What are the properties of hydrogen ? How as re- 
speots respiration ? 




being sixteen times lighter than oxygen, and fourteen times 
and a half lighter than common air. 100 cubic inches of it 
weigh only 2*14 grains. Soap-bubbles blown with it rise 
rapidly in the air ; and it is often employed to fill balloons 
in absence of the cheaper coal gas. A turkey's crop, well 
cleansed, makes a good balloon on a small scale, for the 
class-room, and very beautiful small balloons (from 1} to 5 
feet diameter) are prepared in Paris of gold-beaters' skin. 

396. Hydrogen is the most attenuated as well as the 
lightest form of matter with which we are acquainted. We 
have reason to suppose the molecules of this body to be 
smaller than those of any other now known to us. Dr. 
Faraday, in his attempts to liquefy hydrogen, found that it 
would leak freely with a pressure of 27 or 28 atmospheres, 
through stopcocks that were perfectly tight with nitrogen 
at 50 or 60 atmospheres. This extreme tenuity, together 
with the remarkable law of diffusion of gases 
already explained, (147,) renders it unsafe to 
keep this gas in any but perfectly tight ves- 
sels. A small crack in a bell-jar, quite too 
narrow to leak with water, will soon render 
the hydrogen with which it may be filled ex- 
plosive. The superiority in diffusive power 
which hydrogen has over common air, is well 
seen in what is called Mr. Graham's diffusion 
tube, of which a figure is annexed. A glass 
tube, 11 or 12 inches long, (fig. 282,) and of 
convenient size, has a tight plug of dry plaster 
___ of Paris at the upper end, and being filled 
Fie. 2a2. w ^ ^ rv hydrogen by displacement of air, and 
its lower end put into a glass of water, the 
hydrogen escapes so rabidly through the plaster plug, that 
the water is seen to rise in the tube, so as in a few mo- 
ments to replace a considerable portion of the hydrogen, and 
the remaining portion of gas is found to be explosive. 
Hydrogen also enters into combination in a smaller propor- 
tionate weight than any known body, (238,) and consequent- 
ly has been chosen as the unit of the scale of equivalents. 

What of its density ? What the weight of 100 cubic inches ? What 
nse is made of its levity ? 396. What is the tenuity of hydrogen ? Gire 
Ulustrations from Faraday ? What is Graham's diffusion tube ? What 
of the atomic weight of hydrogen ? Why has it been adopted as unity ? 





807. Hydrogen is a most eminently combustible gas, tak. 
ing fire from a lighted taper, which is instantly extinguished 
by being plunged into the gas. It burns with a bluish-white 
flame and a very faint light. A drj bottle with its mouth 
downward (fig. 283) is well suited to collect this gas by dis- 
placement of air, as the heavier gases are collected 
by the reverse position. When lighted, the gas 
burns quietly at the mouth of the bottle; and 
the extinguished taper may be relighted by the 
flame at the mouth. If the bottle is suddenly re- 
versed after the gas has burned awhile, the remain- 
ing gas, being mixed with common air, will burn 
rapidly with a slight explosion. Three of the most 
remarkable properties of hydrogen are thus shown 
by one experiment, viz. its extreme levity, its 
combustibility, and its explosive union with oxygen. 
If this gas is incautiously mingled with common 
air, or much more, with pure oxygen, a severe ex- 
plosion results when the mixture is fired. The g ' 
eyes or limbs of inexperienced operators have thus too often 
paid the forfeit of carelessness by the explosion of glass ves- 
sels. Particular caution is required not 
to employ any gas until all the common 
air is expelled, as well from the gene- 
rator, as from the receiving-vessel or gas- 

398. Water is the sole product of the 
combustion of hydrogen. The production 
of water from this combustion, and cer- 
tain musical tones, are neatly shown by 
an arrangement like fig. 284. The gas is 
generated in the bottle a, and a perforated 
cork at the mouth has a small glass tube, 
from the narrow end of which the stream 
of hydrogen is lighted. An open glass tube 
Fig. 284. ^ a bout two feet long, held over this flame, 
is at once bedewed by the water produced in the 
combustion, and a musical tone is also generally 
heard. This arises from the interruption which the 
flame suffers from the rapid current of air ascendiDg g * 

397. Give illustrations of its combustibility. What happens if it ii 
mixed with air? What caution is required? 398. What is the produot 
•f its combustion ? What happens if it is burned from a jet in a tuba ? 




through the tube, causing it to flicker, and being moment* 
arily extinguished, there occur a series of little explosions, 
so rapid as to give a tone. The pitch of the note produced, 
depends on the length and size of the glass chimney (fig. 
285) and the size of the jet of hydrogen, which should be 
small. If the jet is fitted to the gas-holder, we can modulate 
the tone by regulating the supply of gas with the stopcock. 
The little gas bottle (fig. 284) is often called the "philoso- 
pher's lamp." 

Compounds of Hydrogen with Oxygen. 

899. There are two known compounds of hydrogen with 
oxygen, viz. : 

Water (the oxyd of hydrogen) HO 

Binoxyd of hydrogen HOt 

The first of these is the most remarkable compound known, 
whether we contemplate it in its purely chemical relations, 
or in reference to the wants of man and the present condition 
of the globe. 

400. Water. — The student has already become familiar 
with the composition of water, as formed by the union of 
two volumes of hydrogen and one of oxygen. In examining 
the compounds of hydrogen and oxygen, as in all other 
chemical investigations, we can pursue the subject either 
analytically or synthetically; that is, we can either form the 
compounds by the direct union of the elements, or we can 
decompose these compounds, and thus gain a knowledge of 
their constitution. 

The simplest case of the decomposition of water is that 
where metallic potassium, or sodium, is employed. The 
potassium, from its great affinity for oxygen, 
takes it from the water, (fig. 286,) and the 
hydrogen escaping, is burned. If sodium is 
introduced into an inverted test-tube under 

"' jT water, the hydrogen is collected. The reao- 

Flg * 286 ' tion is K+HO=KO+H. 

401. The voltaic decomposition of water (224) is, however, 
by far the most satisfactory experiment to this point which 

IIow is this explained ? 399. What compounds does hydrogen form 
with oxygen? 400. What of the constitution of water? What is the 
simplest case of its decomposition ? Hew does potassium effect this ? 





Fig. 288. 

we possess, since both ele- 
ments of the water are 
evolved in a pure form 
and in exact atomic pro- 
portions by volume and 
weight, (fig. 287.) In fact, 
this is a complete experi- 
mentum crucis, being both 
analysis and synthesis; for 
+we may so arrange the 
single tube apparatus (fig. 
288) that the mixed gases 
Fig. 287. from the electrolysis of 
water may be fired by an electric spark, 
as soon as a sufficient volume of the ' 
mixture has been collected. A complete 
absorption follows the explosion, and 
the gases again go on collecting. Platinum, heated very 
hot, decomposes water, and both gases are evolved: this 
happens when vapor of water is passed through a tube of 
platinum heated .to intense whiteness. 

402. What potassium and sodium accomplish at ordinary 
temperatures, is accomplished by iron, only at a red heat. 
The experiment figured in fig. 289 was devised by Lavoisier : 
an iron tube, (as a gun- 
barrel,) or better a tube 
of porcelain, protected by 
an exterior tube of iron, 
heated in a furnace to full 
redness. The tube contains 
clean turnings of iron, or 
better a bundle of clean 
iron wire of known weight. 
A small retort a, holding a Fig. 289. 

little water, is boiled by a spirit-lamp at the moment when the 
tube is at a full red-heat : the vapor of the water coming into 
contact with the heated iron is decomposed, the oxygen is 
retained by the iron, forming oxyd of iron, and the hydro- 
gen is given off from the tube /, which may be made to 
conduct it to the pneumatic trough. For every eight 

401. What of the voltaic decomposition of water ? How does platinum 
decompose water? 402. Describe Lavoisier's experiment, fig. 289. What 
becomes of the oxygen ? 




grains of weight acquired by the iron, 46 cubic inches of 
hydrogen, weighing one grain, have been evolved. 

403. The iron in this case is evidently substituted for the 
hydrogen, taking its place with the oxygen to form the oxyd 
of iron, while the hydrogen is set free. The oxyd of iron 
resulting from this action, is the same black oxyd which the 
smith strikes off in scales under' the hammer, being a mix- 
ture of protoxyd and peroxyd. This case of affinity is an 
interesting one, because it is seemingly reversed when, under 
the same circumstances, we pass a stream of hydrogen over 
oxyd of iron. The iron is then reduced to the metallic state, 
and water is produced. It will be remembered that we cited 
this instance (270) while speaking of the influence of quantity 
of matter in determining the nature of the chemical changes 
which might take place among bodies. 

Referring to the case (393) of sulphuric or chlorohydrio 
acids and zinc, we cannot fail to observe the similarity of 
the two cases of decomposition. That water, or the oxyda- 
tion of a base, is not essential to the evolution of hydrogen 
is conclusively shown in the case of dry chlorohydrio acid 
(HC1) and zinc, which evolve hydrogen, when no compound 
containing oxygen is present: HCl+Zn=ZnCl+H. 

404. Zinc and iron do decompose water even without the 
aid of an acid, but only with great slowness, and the action 
ceases as soon as the metal is covered by the coating of the 
oxyd thus formed, which protects it from further corrosion. 
A dilute acid removes this coating of oxyd, and also aids, 
no doubt, in establishing such electrical relations as to make 
the zinc highly electro-positive. That this is the fact seems 
quite probable, because pure zinc is hardly affected by dilute 
acids, and we have already noticed the effects of amalgama- 
tion (191) in rendering the zinc incapable of decomposing 

Much mystery formerly hung over this case of chemical 
action, which is quite cleared away by the view now pre- 
sented. It was formerly said that the presence of an acid 
in water with zinc disposed the zinc to decompose the water. 
This is what was meant by " disposing affinity/' But there 
can be no oxyd of zinc to exert this influence on the acid, 

403. Wbat is tbe theory of the process ? Why is this an interesting 
ease of affinity ? What similarity is noticed with a previous case ? 404. 
Wbat of the slow decomposition of water by zinc ? What view was held 
formerly? What of disposing affinity? 




Until the water is decomposed ; so that the idea that the 
acid disposed the zinc to decompose the water is quite futile. 

405. The real nature of hydrogen was for a long time 
not well understood. It was associated with oxygen and 
chlorine, because it was supposed to bear the same relations 
to chlorohydrio acid, that oxygen bears to sulphuric and 
ahloric acids. It is now known that hydrogen is most closely 
allied to the metals, particularly to zinc and copper ; that 
the chlorids, iodids, and fluorids of hydrogen, although they 
possess the characters which we assign to acids, resemble in 
many respects the chlorids, iodids, &c., of the same metals; 
that in met, hydrogen is a metal exceedingly volatile, proba- 
bly standing in that respect in the same relation to mercury, 
that mercury does to platinum, but still possessed of all truly 
chemical peculiarities of the metallic state, and no more 
deprived of the commonplace qualities of lustre, hardness, 
or brilliancy, than is the mercurial atmosphere which fills the 
apparently empty space in the barometer tube. (Dr. Kane.) 
The vapor of mercury, and of other volatile metals, is, like 
hydrogen, a non-conductor of heat and electricity; but we 
cannot on this account deny their metallic character. We 
must not forget, moreover, that hydrogen may yet, by suffi- 
cient cold and pressure, be made fluid or solid, when doubt- 
less we shall see its resemblance in physical, as well as we 
now do in chemical characters, to the metals. The propriety 
of assigning to hydrogen the place in our classification which 
it occupies, will thus be more apparent to those who have 
usually seen it placed next to oxygen. 

406. *A mixture of oxygen and hydrogen gases will never 
unite under ordinary circumstances of temperature and pres- 
sure ; but the passage of an electric spark through them, or 
the application of red-hot flame, or an intensely heated wire, 
will produce an explosive union, destructive to the contain 
ing vessel, unless the gas is in extremely small quantities. 
The re*composition or synthesis of water, was proved in tho 
experiment in t he-single cell decomposing apparatus, (fig. 
288.) If that explosion had taken place in a dry vessel over 
mercury, the interior would have been bedewed with moisture 
from the regenerated water. This may be done, as in fig. 

405. What is said of the real nature of hydrogen ? What reasons exist 
for supposing it a metal ? 406. How is the union of hydrogen and oxygan 





290, where a strong glass tube 
t is divided into equal parts, 
for convenience of measuring, 
and supported firmly in the 
mercury vase v. An electrical 
spark from the Leyden vial I is 
made to pass through the gas- 
eous mixture by means of the 
platinum wires p soldered into 
the walls of the upper part of 
the tube. Such an arrange- 
ment is an eudiometer, some 
allusion to which was made in 
832. Hydrogen furnishes us 
the most convenient means of 
analysis of gases containing 
oxygen, by combining with it 
to form water. In eudiometri- 
cal analysis it is always from 
the volume that the result of 
the analysis is deduced, and not, 
Fig. 290. ag j n cagQ f solids, from the 

weight A very good form of eudiometrical tube is that of 
Dr. Ure, (fig. 291.) It is a graduated tube, closed as before 
at one end, and bent on itself. When used, 
it is filled with dry mercury, by placing 
it horizontally in the mercury trough. A 
portion of the gaseous mixture to be de- 
> tonated is then introduced, the thumb 
placed over the open end, and all the mix- 
ture adroitly transferred to the closed limb. 
The mercury is made to stand at the same 
level in both limbs, by forcing out a por- 
tion with a glass rod thrust in at the full 
side. These adjustments being made, the 
whole bulk of the mixture is read on the 
graduation, and while the thumb is firmly 
held over the open end of the tube, an 
electrical spark is made to explode the 
Fig. 291. eases. The air between the thumb and 

Describe fig. 290. How is hydrogen useful in gas analysis ? What if 
lire's eudiometer? How is it used? 





die mercury acts like a spring to break the force of the ex- 
plosion ; and afterward, on removing the thumb, the weight 
of the atmosphere forces the mercury into the shorter leg, 
to supply the partial vacuum occasioned by the union of the 
gases. Proper allowances being made for temperature and 
pressure, the quantity of residual gas is read on the gradua- 
tion, and a calculation can then be made of the amount of 
oxygen present. If the gas contains carbon, carbonic acid 
would be formed, and must be absorbed by potash solution. 

407. Volta's eudiometer, represented in fig. 292, 
is a very complete instrument for gas analyses 
over the pneumatic-trough. In this instrument 
the explosion is made in a thick glass tube A 8, 
into which the electrical spark is passed by t. The 
graduated measure p screws into the funnel D, and 
is used to measure the portion of gas to be deto- 
nated, which is poured in by the funnel at 
bottom. Before use, the tube P is removed, the 
cocks R and S are both opened, and the whole in- 
strument sunk in the cistern until it is entirely full 
of water. The cock R is then shut, the portion 
of gas measured in P and introduced by C, the cock 
S closed, and explosion made. If any residue re- 
mains, its quantity is measured by opening It, 
when it rises into P, previously filled with water, . 
and its quantity is read off on the graduation. 
The metallic strap p serves as a communication 
for the electric circuit, and also as a scale of equal 
parts for ruder measurements of gas. This instru- 
ment is well adapted for rapid class illustration, 
in the lecture room, and is applicable in all eu- 
diometrical experiments in which gaseous analysis 
is to be performed by oxygen and hydrogen. For 
accurate research, the beautiful eudiometer of 
Regnault is the most reliable instrument. 

408. The explosion of oxygen and hydrogen gases, when 
mingled in atomic proportions, is very severe, and can be 
performed safely only on very small volumes of the gases, 
or in strong vessels of metal. The ingenuity of the demon- 
strator will devise many instructive and amusing experi- 

H'*w is the carbonic acid removed? 407. What is Volta's eudiometer? 
How is it used ? 408. What illustrations are given of the severity of the 
explosion of oxygen and hydrogen ? 


Pig. 292. 




ments depending on the explosion of this mixture. The 

r pistol, and hydrogen-gun, (fig. 293,) a blad- 
filled and fixed from a pin-hole or by an 
electric spark, soap-bubbles, and other familiar 
• illustrations, all give evidence of the energy of 
the action by which water is formed from die 
union of its elements. The explosion is probably 
due to the rush of air consequent on the sudden 
expansion and immediate condensation of a vo- 
Fig. 293. lume of steam formed at the most intense heat 
which can be produced by art. 

The union of oxygen and hydrogen can, however, be ef- 
fected slowly and quietly, without any explosion or visible 
combustion. This is accomplished by passing the mixed 
gases through a tube heated below redness ; and at a still 
lower temperature, if the tube contains coarsely powdered 
glass or sand. We see in this case an instance of that re- 
markable phenomenon called " surface action/' (251) be- 
fore alluded to. 

409. Professor Dobereiner, of Jena, observed, in 1824, 
that platinum in the state of fine division, known as spongy 
platinum, would cause an immediate union of these gases. 
A drop of strong chlorid of platinum evaporated on writing 
paper, and the paper burned, gives platinum in that state, 
and such a pellet of paper may be prepared in an instant 
and used to fire hydrogen. The common instrument 
employed for lighting tapers is made by taking advantage 
of this principle. A little spongy platinum is formed into 
a ball, and mounted on a ring of wire (fig. 294) 
which slips within the cup d on the top of gas- 
holder a (fig. 295.) The gas is generated by the 
action of dilute acid in the outer vessel a on a 
lump of zinc z hanging in the inner vessel /, and 
Fig. 294. j g j et ont at pi easure by the cock c, issuing in a 
stream on the spongy platinum. The latter is at once 
heated to redness by the stream of hydrogen, which is con- 
densed within its pores to such a degree that it combines 
with a portion of oxygen, always present in the sponge by 
atmospheric absorption. The union of these gases is attended 
by intense heat, and, as a consequence, the platinum at once 
glows with redness, and the hydrogen is inflamed. After 

How is this union effected slowly ? 409. What was the observation oi 
Dobereiner? Describe the hydrogen lamp ? 





tome time the sponge loses this property to 
a certain extent, but it is again restore' ~ 
being well ignited. When the spongy 

tinum is mixed with clay and sal-ammoniac 
made into balls and baked, its effects are less 
intense, and such balls are often used in analy- 
sis to cause the gradual combination of gases. 
Faraday has shown that clean slips of pla- 
tinum foil, and even of gold and palla- 
dium, can effect the silent union of hydro- < 
gen ana oxygen. For this purpose the pla- 
tinum is cleaned in hot sulphuric acid, washed 
thoroughly with pure water, and hung in a jar ls * 
of the mixed gases. Combination then takes place so ra- 
pidly as to cause at every instant a sensible elevation of the 
water in the jar. If the metal is very thin, it sometimes 
becomes hot enough during the process of combination to 
glow, and even to explode the gases. 

410. The same effect of platinum in causing combination 
is seen in other bodies besides oxygen and hydrogen. Seve- 
ral mixtures of carbon gases will act with platinum in the 
same way ; and the vapors of alcohol or ether 
may be oxydized by a coil of platinum wire 
hung from a card in a wineglass (fig. 296) 
containing a few drops of either of these 
fluids. The coil of wire is heated to red- 
ness in a lamp, and, while still hot, is hung 
in the glass ; it then, if air has free access, 
retains its red-hot condition as long as any 
vapor of ether or alcohol remains. In this 
case, only the hydrogen of the ether, or al- 
cohol, is oxydized, and the carbon is unaf- 
fected ; a peculiar irritating acid vapor is given off, which 
affects the nose and eyes unpleasantly. Little balls of pla- 
tinum sponge suspended over the wick of an al- f\ 
cohol lamp will, in like manner, glow for hours I 
after the lamp is extinguished. A spirit-lamp fed 
with alcoholic ether will cause the coil of plati- 
num wire (fig. 297) to glow for hours in the same 
way, constituting what has been called the aphlb- 
gistic lamp. 

What has Faraday shown on this point ? 410. How does platinum 
act on vapors ? What is the aphlogistio lamp ? 

Fig. 296. 

Fig. 297. 





411. The oxyhydrogen blowpipe of Hare enables tbt 
chemist to use safely the intense heat produced by the com- 
bustion of oxygen and hydrogen. In Dr. Hare's instru- 
ment the two gases were brought from separate gas-holders 
and mingled only in the moment of contact. The flame of 
the oxyhydrogen blowpipe differs from the flame of a lamp 
or candle by being, so to speak, a cone of aerial matter en- 
tirely ignited in every part, while the flame of a candle is 

ignited only on the outside, 
(460.) The structure of 
the jet contrived by Profes- 
sor Daniell illustrates this, 
Fig. 298. where the oxygen tube o is 

seen (figure 298) to pass 
through that carrying the hydrogen, H. Thus the combus- 
tible gas is in contact with the oxygen to burn it both from 
the air and from the instrument. The let may be pro- 
vided with a cock (fig. 299) and connected with the gas- 
holders by two flexible pipes attached at and H. The 

Fig. 299. 

Fig. 301. 

Fig. 300. 
gas-holders may conveniently be 
made of impervious caoutchouc cloth, 
arranged with pressure boards, and 
weights as in fig. 300, an arrange- 
ment which admits of convenient 
transportation and dispenses with 
the use of water. The gas is ad- 
mitted and expelled by the flexible 
pipes p and controlled by the cocks c. 
The effects of the compound blow- 
pipe may also be safely produced 
by passing a stream of oxygen from 
a gas-holder (fig. 301) through the 

411. What is Hare's blowpipe ? How does its flame differ from common 
flames ? How is the jet fig. 298 constructed ? How are the gases disposed ? 





flame of a spirit-lamp w. The jet is regulated by the cock 
I, while the lamp-flame supplies the hydrogen. 

412. The mixed gases, in atomic proportions, are some- 
times forced by a condensing syringe into a very strong 
metallic box, from which they issue by their 
own elasticity. To prevent the danger of 
explosion, a contrivance is employed called < 
" Hemming's safety tube." This is a brass ( 
tube, six or eight inches long, filled with fine 
brass wire, closely packed, and having a coni- i 
cal rod of brass forcibly driven into their 
centre, by which the wires are very closely 
crowded together. This forms in fact a great 
number of small metallic tubes, through which 
the gas must pass. It is a property of such 
small tubes entirely to arrest the progress of 
flame as we shall presently see. (Safety 
lamp of Davy, 464.) The jet is screwed to < 
one end of this tube, and the other end is 
connected with the holder of the mixed gases. Fig. 302. 
Several severe explosions, it is said, have occurred, even with 
all these precautions ; so that if the mixed gases are used 
at all, it should only be in a bag or bladder, the bursting 
of which can be attended with no danger. 

413. The effects of the compound blowpipe are very 
remarkable. In the heat of its focus the most refractory 
metals and earths are fused, or dissipated in vapor. Plati- 
num, which does not melt in the most intense furnace of the 
arts, here fuses with the rapidity of wax, and is even vola- 
tilized. Even those metallic oxyds, as lime, magnesia, and 
alumina, which are entirely infusible in any other artificial 
heat, yield to this focus. By the adroit management of the 
keys, which a little practice soon teaches, we can either re- 
duce metallic oxyds, or oxydize substances still more highly. 
The flame of the mixed gases falling on a cylinder of pre- 
pared lime, adjusted to the focus of a parabolic mirror, pro- 
duces the most intense artificial light known. This is what 
is called the Drummond light. It is extensively employed in 
distant night-signals, and can be seen farther at sea than any 

412. How are the mixed gases burned safely? What is Hemming's 
safety jet? 413. What are the effects of the compound blowpipe* 
What it the Drummond light ? 




other light. It is also used as a substitute for the sun's light 
in optical experiments. The galvanic focus alone, among 
artificial sources of light, surpasses it, (200.)* 

History of Water. 

414. Water, when pure, is a colorless, inodorous, tasteless 
fluid, which conducts heat and electricity very imperfectly, 
refracts light powerfully, and is almost incapable of com- 
pression. We have already made so much use of water, in 
illustration of the laws of heat and of chemical combina- 
tion, in the former part of this volume, that the student 
must already be familiar with many of its attributes. Its 
greatest density, it will be remembered, (103,) is found to 
be at 39°*5, or, more exactly, 39°-83. It is the standard 
of comparison (33), for all densities of solids and liquids. 
In the form of ice, its density is 0-94, and at 32° it freezes. 
One imperial gallon of water weighs 70,000 grains, or just 
ten pounds. The American standard gallon holds, at 
39°-83 Fahr., 58,372 American troy grains of pure distilled 
water. One cubic inch, at 60° and 30 inches barometer, 
weighs 252yy^ grains, which is 815 times as much as a like 
bulk of atmospheric air. One hundred cubic inches of 
aqueous vapor, at 212° and 30 inches barometer, weigh 
14-96 grains, and its specific gravity is 0*622. Water 
boils under ordinary circumstances at 212°; but we have 
seen that its boiling point was very much afFected by the 
nature of the vessel. It evaporates at all temperatures. 

415. The conversion of water into ice is attended with 

On toJttm *i$fou fc ^ exerc * se °f crystallo- 

^K SlPii rail? & en * c attractions, although 
1 |P* ^fir the resulting forms are 

Fig- 303. rarely visible. But in 

snow we often see beautifully grouped compound crystals, 
resulting from the union of forms derived from the hexago- 
nal prism. Figure 303 gives some of the more simple of 

414. What are the properties of water ? What the temperature of itt 
greatest density ? What the density of ice ? What that of a cubio 
inch ? of a gallon ? of its vapor ? 415. What is said of the crystalliza- 
tion of water? 

* Mr. E. N. Kent, of New York, furnishes a very efficient and cheap form 
of compound blowpipe, with gas-bags and Drummond light apparatus. 





these forms. The laws of congelation of water have already 
been fully explained, 123. 

416. Pare water is never found on the surface of the 
earth; for the purest natural waters, evaporated to dryness, 
leave always a visible residue, containing small quantities of 
earthy or saline matters which have been dissolved from the 
rocks and soil. Moreover, all good water — that which is 
fit for the use of man — has a considerable quantity of car- 
bonic acid and atmospheric air dissolved in it, (332,) and 
without which it would be flat and unpalatable. 
A jar of spring water placed under a bell on the 
air-pump (fig. 304) will appear to boil as the 
exhaustion proceeds from escape of the dissolved 
air. It is upon this air that the fish and other water- 
breathing animals depend for life ; and conse- 
quently, when a vessel containing fish is placed < 
on the air-pump and the air exhausted, the fish are 
seen soon to give signs of discomfort, (fig. 305,) 
and will die if the operation is continued. 
Many mineral springs, besides the saline 
matters they hold in solution, are highly 
charged with sulphuretted hydrogen, car- 
bonic acid, and other gases derived from 
chemical changes going on in the beds 
from which they flow. 

Pure water can be procured only by 
distillation, and it is a substance of such 
indispensable importance to the chemist,! 
that every well-furnished laboratory is pro- 
vided with means for its abundant prepa- 
ration. A copper still, well tinned, and connected with a 
pure block-tin worm or condenser, answers very well to pro- 
duce the common supply. • But very accurate operations 
require it to be again distilled in clean vessels of hard glass. 

417. The solvent powers of water far exceed those of 
any other known fluid. Nearly all saline bodies are, to a 
greater or less extent, dissolved by water, and heat generally 
aids this result. In the case of common salt, however, 
and a few other bodies, cold water dissolves as much as hot. 

What depends on the presence of air in the water ? What other 
gases are found in it ? How is pure water obtained ? 416. What fo- 
reign substances aro found in water ? How is the air in water shown ? 
Why important to animal life ? 417. What are the solvent powers of water ? 





The solvent powers of pure water are generally greater 
than those of common water. 

Gases are nearly all absorbed or dissolved in cold water, 
and some of them to a very great extent, while others, as 
hydrogen and common air, very slightly. Hot water dis- 
solves many bodies which are quite insoluble in cold, 
especially when aided by small portions of alkaline matter. 
The waters of the hot springs in Iceland and Arkansas de- 
posit much silicious matter before held in solution ; and Dr. 
Turner found that common glass was dissolved in the cham- 
ber of a steam-boiler at 300°, and stalactites of silica were 
formed from the wire basket in which the glass was sus- 

418. Water always absorbs the same volume of a given 
gas, whatever may be its density : thus, of carbonic acid, 
of ordinary tension, it dissolves its own volume ; it would do 
no more if the gas were reduced to half its first density ; and 
it dissolves the same volume when the pressure is at 30 
atmospheres. Hence water which has absorbed gases under 
pressure, parts with them in effervescence when that pressure 
is removed. Again, if a mixture of gases is present at a 
given tension, water absorbs of each the same volume as it 
would take up if only that one was present. Such, it will 
be remembered, is the fact with regard to the gases of the 
atmosphere, (332.) Gases dissolved in water are all ex- 
pelled by boiling. If, 
therefore, we would 
know what- volume 
of a given gas was 
dissolved in water, 
the fact is accurately 
determined by boiling 
a measured quantity 
in a flask quite full, 
as in figure 806, and 
conveying the escap- 
ing gas by a bent tube 
(also previously filled 
with water) to a gra- 
duated jar on the 

Fig. 306. 

What of the action of hot water ? 418. What volume of gases does 
water absorb ? How does pressure affect this ? How of mixed gases ? How 
is the volume of gases contained in water determined? Describe fig. 306. 




mercurial cistern. We then measure the volume of gas ex* 
pelled directly. 

419. The powers of water as a chemical agent are very 
various and important. From its neutral, mild, and salu- 
tary character, we are accustomed to regard it only as a 
negative substance, possessed of little energy, while it is in 
fact one of the most important chemical agents in our pos- 
session. Besides its solvent powers, we know that it com- 
bines with many substances, forming a large class of hy- 
drates: hydrate of lime and potash are examples. It is 
also, as we have seen, (320,) essential to the acid properties 
of common sulphuric, phosphoric, and nitric acids, acting 
here the part of a much more energetic base than in the hy- 
drates. It forms an essential part in the composition of 
many neutral salts, and can be replaced in composition by 
other neutral saline bodies ; while as water of crystallization 
it discharges still another important and distinct function, 
the crystalline forms of many salts being quite dependent 
on its presence in atomic proportions. Of organic struc- 
tures, both animal and vegetable, it forms by far the most 
considerable constituent. Its vapor at high temperatures 
displaces some of the most powerful acids, as Tilghmann has 
shown, in his patent process for procuring the alkaline bases 
by decomposing their sulphates, chlorids, and even, to some 
extent, silicates, by vapor of water at a high temperature. 
Sulphate of lime, for example, so treated, has all its sul- 
phuric acid driven off as S0 3 , and caustic lime is left behind. 
The geological importance of these facts can hardly be over- 

420. Peroxyd or Binoxyd of Hydrogen. — This curious 
compound was discovered in 1818, by M. Thenard. It is 
obtained in decomposing the peroxyd of barium by as much 
very cold solution of hydrofluoric acid (fluosilicic or phos- 
phoric acid may be used as well) as will exactly saturate 
the base, the whole being precipitated as fluorid of barium. 
The reaction may be expressed thus : 

Peroxyd of barium. Fluohydric add. Fluorid of barium. Peroxyd of hydrogen. 

BaO a + HF = BaF + HO a . 
The peroxyd of hydrogen remains dissolved in the water, 
which is freed «from the insoluble fluorid of barium by filtra- 

419. What are the chemical powers of water ? What is crystallization- 
water? What are Tilghmann's experiments? 420. What is the per- 
oxyd of hydrogen ? How procured ? Give the reaction. 





lion, and then evaporated in the vacuum of an air-pump by 
the aid of the absorbing power of sulphuric aeid. 

421. Properties. — The properties of this body are very 
remarkable. When as free from water as possible, it is a 
syrupy liquid, colorless, almost inodorous, transparent, and 

possessed of a very nauseous, astringent, and disgusting taste. 

ts specific gravity is 1*453, and no degree of cold has ever 
reduced it to the solid form. Heat decomposes it with effer- 
vescence and the escape of oxygen gas. It can be preserved 
only at a temperature below 50°. The contact of carbon and 
many metallic oxyds decomposes it, often explosively, and 
with evolution of light. No change is suffered by many 
bodies which decompose it; but several oxyds, as those of 
iron, tin, manganese, and others, pass to a higher state of 
oxydation. Oxyd of silver, and generally those oxyds 
which lose their oxygen at a high temperature, are reduced 
to a metallic state by this decomposition. When diluted, 
and especially when acidulated, the peroxyd of hydrogen is 
more stable. It is dissolved by water in all proportions, 
bleaches litmus paper, and whitens the skin. None of its 
compounds are known, nor does it seem to have any ten- 
dency to combine with other bodies. 

Compounds of Hydrogen with the II. and III. Classes. 

422. The eminently electropositive character of hydrogen 
causes it to form well-characterized and analogous com- 
pounds with all the members of the oxygen group. These 
binary compounds have frequently been called the hydracids } 
in distinction from those acid bodies already considered, 
which, in parity of language, have been called the oocacids. 

It is, however, more in accordance with facts and the 
principles of a philosophic classification, to look upon these 
bodies as having in reality the same essential characters as 
the chlorids, bromids, iodids, &c, of other electro-positive 
bases. The principles of our nomenclature require these 
compounds to be called after their electro-negative elements, 
t. e, chlorohydric acid, bromohydric acid. Their general 
formula is HE. The compounds of hydrogen to be con- 
sidered under this head are — 

421. "What are its properties ? 422. What are the hydracids ? What 
view is taken of their constitution ? What compounds are enumerated 
under this head ? What is their general formula ? 




Solphydric aoid HS 

Selenhydrio acid. HSe 

Tellurhydrio acid HTe 

CMorobydric acid. HOI 

. Bromohydrio acid. HBr 

lodohydric acid HI 

' Fluohydric acid. HF 

423. Hydrogen and chlorine, mingled in the gaseous 
state, combine with explosion by the touch of a match, 
forming chlorohydric acid. The rays of the sun effect the 
same result instantaneously, while in diffuse light combina- 
tion follows in a gradual manner and quietly. In the dark, 
no union occurs, showing that light in this case plays the 
part of heat, and impresses, as we shall see, a peculiar con- 
dition on chlorine. If two vessels of equal 
Capacity (fig. 307) are filled, the one, A, with 
dry hydrogen, the other, B, with dry chlo- 
rine, by displacement, and are then united, 
as seen in the figure, on exposing them with 
precaution to the sun's direct rays, an im- 
mediate explosion follows. Dr. Draper has 
shown that chlorine gas which had been ex- 
posed alone and dry to the sun's light ac- 

quired the power of forming this explosive _,. 307 
union with hydrogen, even in the dark, and lg * 

retained it for some time; while, on the other hand, chlorine 
prepared in the dark manifests no avidity for hydrogen un- 
less exposed to the light. This fact was before mentioned 
(288) when speaking of the active and passive conditions 
of chlorine. In its passive state, (as prepared in the dark,) 
it actually replaces hydrogen in the constitution of many 
organic bodies, or, in other words, assumes an electro-posi- 
tive condition. The effect of the sun's light is to confer a 
new state upon it, probably by a new arrangement of its 
molecules, by which its character is completely changed. 
It then apparently becomes highly electro-negative. 

The decomposition of water by chlorine (288) evinces its 
strong affinity for hydrogen. Chlorine thus becomes one 
of the most powerful oxydizing agents known, since the 
nascent oxygen given off during the decomposition of water 
attacks with energy any third body which may be present 
that is capable of combining with it. 

424, Chhrohydric Acid, HC1. — If the experiment (fig. 

423. How do chlorine and hydrogen act when mingled? Describt 
fig. 307. What has Draper shown ? What is the passive state of chlo- 
rine ? What relation has it in this state to organic bodies ? On what 
does the decomposition of water by chlorine depend ? 




807) is placed in diffuse light, the green color of the gas is 
seen gradually to diminish and finally to disappear alto- 
gether; and, on opening the junction beneath mercury, no ab- 
sorption occurs, and the vessels are found to be filled with 
chlorohydric acid gas. It appears therefore that this acid if 
formed by the union of equal volumes of the constituent gases 
without condensation. Its density is consequently equal to 
half the sum of the united densities of chlorine and hydro- 
gen, i. e. 2-44 -f -069 = 2-509 -s-2 = 1-254, theoretical den- 
sity of chlorohydric acid gas. Experiment gives 1-2474. 

425. Chlorohydric acid is a colorless, acid, irrespirable 
gas. It forms copious clouds of acid vapor with the moist- 
ure of the air, very suffocating, and irritating the eyes. It 
extinguishes a lighted candle, and is not decomposed by 
electricity. It is very soluble in water, which at 32° takes 
up about 500 times its volume and acquires a density of 
1-21. At a higher temperature it absorbs less. This gas is 
therefore collected over mercury. A bit of ice passed up 
to a jar of it on the mercury cistern, is fused immediately 
by its avidity for water, a dilute solution of chlorohydric 
acid results, and the mercury rises to fill the jar. With a 
pressure of over 26 atmospheres it becomes a colorless liquid, 
which has never been frozen. 

426. Preparation. — For experimental purposes in the 
laboratory it is sufficient to warm the strong commercial 
liquid acid, which parts with a large portion of gas at a gentle 

heat. This may be dried 

by passing it through a 

chlorid of calcium tube. 

The apparatus thus ai- 

ranged is shown in figure 

308. The concentrated 

acid is placed in c and its 

moisture is removed by 

,-the chlorid of calcium 

apparatus a. The weight 
Fig. 308. of tne gas enaD i es U8 to 

collect it by displacement of air in dry vessels b. For 
this purpose it is not usually requisite to dry it. 

In the arts it is always obtained from the decomposition 

424. What is the constitution of chlorohydric acid? What is its theo- 
retical composition and density ? Its experimental ? 425. What are its 
properties ? How soluble in water ? How collected ? 420. How is it 
prepared for experiment in the laboratory ? Describe fig. 308. 





of common salt, (chlorid of sodium, NaCl,) by sulphurie 
acid. The reaction is sufficiently simple : NaCl -f SO t . 
HO = (NaO.S0 8 ) + HC1. The apparatus employed in 
this process is shown in 
fig. 309. Common salt 
is placed in the flask a, 
provided with a safety 
tube / and an eduction 
tube h. The sulphuric 
acid fox decomposing the 
salt is introduced at 
pleasure through/. The 
action is aided by a gen- 
tle heat from the fur- 
nace below. Thechloro- 
hydric acid is rapidly 
evolved and passes into 
c, where it is washed by 
a little warm water and 
thence by e to the last 
bottle d, where it is ab- 
sorbed by the ice-cold 
water which it contains. 
In the middle bottle is 
a tube g f of large size 
and open at both ends, Fi S« 3a9 * 

its lower extremity dips into the wash-water. This 
contrivance prevents the accident which is otherwise 
likely to happen should a partial vacuum occur in a, 
from a cessation of the action ; when the pressure 
of the air on the fluid in d would carry it back into 
c, and finally into a. The safety tube (fig. 310) at- 
tached to the flask a also serves to prevent this acci- 
dent as well as to introduce the* acid. When a liquid 
is poured in at the funnel-top, it must rise as 
high as the turn, before it can pass down into the 
flask, and a portion of the fluid is therefore always 
left behind in the bend, which serves as a valve 
against the entrance of air, and also effectually pre- 
vents an explosion of the flask in case the tube of 
delivery should become stopped. This simple con- lg * 

How is it procured in the arts ? Give the reaction. Describe the appa- 
totus, fig. 309. What is a safety tube ? Describe fig. 310. 





trivance we have often employed but have not before ex* 
plained its action. This same apparatus may be employed in 
making solutions of all the absorbable gases, and is so simple 
as to be within the means of the humblest laboratory ; the 
essential parts being only wide-mouthed bottles, glass tubes, 
a gas bottle or flask, and corks. 

427. Pure chlorohydric acid is procured by distilling the 
commercial acid. The distilling apparatus employed for 
this purpose is seen in fig. 311. The heat is applied by a 
sand-bath beneath the retort. The gas given off is absorbed 
by a little water placed in the last bottle, which is connected 
by a bent tube with the two-necked receiver. If the corn- 

Fig. 311. 

mercial acid is diluted by water until it has the specific gra- 
vity I'll, it no longer evolves acid fumes when heated, and 
the fluid distilled has the same density as that in the retort, 
retaining 16 equivalents of water. 

428. Properties. — Liquid chlorohydric acid is a colorless, 
highly acid, fuming liquid, having when saturated a specific 
gravity of 1-247 : it then contains 42 parts in a hundred of 
real acid. Its purity is tested by its leaving no residue on 
evaporating a drop or two on clean platinum, and by its 
giving no milkiness when a solution of chlorid of barium is 
added to it, (due to sulphuric acid.) Neutralized by 
ammonia, it ought not to become black when hydrosut 

427. How obtained pure? Describe fig. 311. At what density does it 
distill unchanged? 428. What are the properties of the liquid acid? 
What ar* tests of its purity ? 




phuret of ammonium is added, (due to iron.) This acid is 
an electrolyte, and is also decomposed by ordinary elec- 
tricity. A mixture of muriatic acid gas with oxygen, passed 
through a red-hot tube, produces water and chlorine. The 
commercial acid is always impure, and colored yellow by 
free chlorine, iron, and organic matters. 

Tate. — A solution of nitrate of silver detects the pre- 
sence of a soluble chlorid, or of chlorohydric a/jid, 
by forming with it a whito curdy precipitate of 
chlorid of silver, which is soluble in ammonia, 
but insoluble in acids or water. A rod a, if dip- 
ped in ammonia and held over a glass containing 
chlorohydric acid, gives off a dense white cloud 
of chlorid of ammonium. Fi «- 312 - 

429. The uses of chlorohydio acid are very numerous. 
Its decomposition by oxyd of manganese affords the easiest 
mode of procuring chlorine, (282.) It dissolves a great 
number of metals and oxyds, forming chlorids, from which 
these metals may be obtained in their lowest state of 
oxydation. In chemical analysis and the daily operations 

. of the laboratory it is of indispensable use. 

Chlorohydric acid is made in the arts in immense quanti- 
ties, especially in England, where the carbonate of soda is 
largely made from common salt (chlorid of sodium) by 
the action of sulphuric acid. Mingled with half its own 
volume of strong nitric acid, it makes the deeply colored, 
fuming, and corrosive aqua-regia. This mixed acid evolves 
much free chlorine, which in its nascent state has power to 
dissolve gold, platinum, &c, forming chlorids of those 
metals, and not nitromuriates as was formerly supposed. 
As soon as all the chlorine is evolved, this peculiar power 
of the aqua-regia is lost. 

430. Bromohydric Acid, HBr, Bromid of Hydrogen. — 
Hydrogen and bromine do not act upon each other in the gase- 
ous state, even by the aid of the sun's light; but a red heat 
or the electric spark causes union — only among those parti- 
cles, however, which are in immediate contact with the heat, 
the action not being general. Bromohydric acid may be 
prepared by the reaction of moist phosphorus on bromine in 
a glass tube (fig. 313.) The gas given off must be collected 

What tests are named ? 429. What are its uses ? What is aqua-regia t 
430. What is bromohydric acid ? How prepared ? 




over mercury. It is composed, like chlorohydric acid, of 
equal volumes of its elements not condensed. Its specific 
gravity is 2*731, and it is condensed by cold and pressure 
into a liquid. In its sensible properties it bears a close re- 
semblance to chlorohydric acid. With the nitrates of silver, 
lead, and mercury, it gives white precipitates similar to the 
chlorids. It has a strong avidity for water, and dissolves 
largely in it, giving out much heat during the absorption. 
The saturated aqueous solution has the same reactions as the 
dry acid, and fumes with a white cloud in contact with air. 
It dissolves a large quantity of free bromine, acquiring 
thereby a red tint. 

431. Iodohydric Acid. — This body may be formed by 
the direct union of its elements at a red-heat, but is 
more easily prepared by acting on iodine and water with 
phosphorus, by which means the gas is formed in large 
quantities. The action of phosphorus and iodine is violent 
and dangerous, but may be regulated and made safe by 
putting a little powdered class between each layer of phos- 
phorus and iodine, (fig. 313.) Phos- 
phoric acid is formed and remains in, 
solution, while the iodohydric acid 
gas is given out, and may be col- 
lected over mercury, or dissolved 
in water. The dry gas has a great 
avidity for water. Its specific 
gravity is 4*443, being formed, like 

> the last two compounds, of one vo- 
Fig. 313. lume of each element uneondensed. 

Cold and pressure reduce it to a 
clear liquid, which, at— 60° Fahr.,freezes into a colorless solid, 
having fissures running through it like ice. It forms a very 
acid fluid by solution in water, which has, when saturated, a 
specific gravity of 17, and emits white fumes. The aqueous 
solution is also prepared by transmitting a current of hydro- 
sulphuric acid through water in which free iodine is sus- 
pended. The gas is decomposed, sulphur set free, and 
hydriodic 2*cid produced, which is purified from free hydro- 
sulphuric acid by boiling, and from sulphur by filtration. 

432. Properties. — The aqueous iodohydric acid is easily 

431. How is iodohydric acid prepared ? What are its properties ? How 
L» it« aqueous solution prepared ? 

Digitized by VjOOQ IC 


decomposed by exposure to the air, iodine being set free. 
It forms characteristic, highly colored precipitates with 
most of the metals, particularly with lead, silver, and 
mercury. Bromine decomposes it, and chlorine decomposes 
both hydrobromic and hydriodic acids, thus showing the 
relative affinities of these bodies for hydrogen. This acid 
is a valuable reagent; its presence in solution is easily 
detected by a cold solution of starch, which, with a few 
drops of strong nitric or sulphuric acid, instantly gives the 
fine characteristic blue of the iodid of starch. 

483. Fluohydric acid is obtained from the decomposition 
of fluor-spar by strong sulphuric acid. The operation must 
be performed in a* retort of pure lead, silver, or platinum, 
and requires a gentle heat. Fig. 314 shows 
Hhe form of retort used for this purpose, the 
junction of the head and body is made tight 
by a lute of gypsum and water, fflrr^ 
ISj^ as any lute containing silica ™%ft 

\^m will be attacked by the fluohy- 

^^ dric acid. The sulphate of 

Fig. 314. i* me regu it m g f rom the action 

forms a solid insoluble mass in the body of 
the retort : hence the necessity of so large an 
opening. The fluohydric acid resulting is 
condensed in a large tube of lead, bent as in Fig. 315. 
fig. 315, so as to enter a refrigerant apparatus : at one end it 
is luted to the beak of the retort, at the other is narrowed 
to a small aperture. The reaction is expressed as follows : 

Bi? SuLacid. ^ul. lime. *ȣ* 

CaF + S0 8 .H0 = S0 8 .CaO + HF 

The fluor-spar employed should be quite free from silica 
and sulphur. 

434. Properties. — Concentrated fluohydric acid is a gas 
which at 32° is condensed into a colorless fluid, with a den- 
sity of 1-069. Its avidity for water is extreme, and when 
brought in contact with it, the acid hisses like red-hot iron. 
Its aqueous solution, as well as the vapor of the acid, attack 
glass and all compounds containing silica very powerfully. It 

432. What are its characters? 433. How is fluohydric acid pre* 
pared ? Describe the apparatus, fig. 314. What is the reaction ? 434. 
What are its properties ? 






(s often used in the laboratory for marking test-bottled or gra- 
duated measures, or biting in designs traced in wax on the 
surface of v glass plates. It is a powerful acid, with a very 
sour taste, neutralizes alkalies, and permanently reddens blue 
litmus. On some of the metals its action is very powerful; 
it unites explosively with potassium, evolving heat and light. 
It attacks and dissolves, with the evolution of hydrogen, cer- 
tain bodies which no other acid can affect, such as silicon, zir- 
conium, and columbium. Silicic, titanic, oolumbic, and mo- 
lybdic acids are also dissolved by it. 

Fluohydric acid, in its most concentrated form, is a most 
dangerous substance. It attacks all forms of animal matter 
with wonderful energy. The smallest drop of the concen- 
trated acid produces ulceration and death, when applied to 
the tongue of a dog. Its vapor floating in the air is very 
corrosive, and should be carefully avoided. If it falls, even 
in small spray, on the skin, it produces an ulcer, which it is 
very difficult to cure. For this reason it is quite inexpe- 
dient for unexperienced persons to attempt its preparation. 
By using a weaker sulphuric acid, however, or by having 
water in the condenser, no risk is incurred. As before re- 
marked, it attacks silica more powerfully than any other 
body. This fact puts us in possession of an admirable mode 
of analyzing silicious minerals, when we do not wish to fuse 
them with an alkali. 

435. Sulphydric Acid ', Sulphuretted Hydrogen. — When 

the protosulphuret 
of iron or the sul- 
phuret of antimony 
is treated with a dilute 
acid, effervescence 
occurs, and a gas is 
given out having a 
most disgusting, fetid 
odor, which at once 
reminds us of the 
nauseous smell of bad 
eggs. This process is 
performed in the evo- 
lution-bottle A, (fig. 

What its uses? What of its safety ? How does it act on the organs? 
What is its great affinity ? 435. What is hydro-sulphuric acid ? What if 
its common name ? 

Fig. 316. 





816) in which a portion of sulphuret of iron is acted on by 
dilate sulphuric acid turned in at the funnel-tube 6. The es- 
caping gas is led by a to the inverted bottle. This operation 
should be performed in a well-drawing flue or in the open 
air. The reaction is FeS+S0 8 +HO=FeO.S0 8 -f HS. 

If sulphuret of antimony is used, heat is needed; and we 
must employ the apparatus fig. 317, and chlorohydric in- 

Fig. 317. # 

stead of sulphuric acid. This mode evolves no free hydro- 
gen, which is present in small quantities when protosul- 
phuret of iron is used. This is sulphuretted hydrogen gas, 
one of the most useful reagents to the chemist, especially in 
relation to the metallic bodies. 

436. Properties. — Sulphydric acid is a colorless gas, of a 
disgusting odor, like that of putrid eggs. Its density is 
1-191, or a little heavier than air. It is liquefied at 50° 
by a pressure of 15 or 16 atmospheres, and at — 122° 
Fahrenheit it freezes into a white confused crystalline solid, 
not transparent, and which is much heavier than the fluid, 
sinking in it readily. Heat partially decomposes it. It 
burns with a blue flame, depositing sulphur on the interior 
of the bottle. Sulphurous acid and water are its products 
of combustion. Mingled with 1£ volumes of oxygen the 
combustion is complete, no sulphur is deposited, and there 

How prepared ? Qive the reaction. Why is sulphuret of antimony 
sometimes preferred ? 436. What are its properties ? Is it combustible 7 
How is it decomposed ? How much oxygen burns it ? What are the pro- 
dustf of combustion ? 




is a shrill explosion. Strong nitric acid also inflamos and 
burns it. Chlorine, bromine, and jodine also decompose it. 
Mingled with a considerable volume of air in contact with 
organic matter, it slowly forms sulphuric acid. It is a true 
but feeble acid. 

Water, if cold, and recently boiled, dissolves 2} or 3 timet 
its volume of sulphydric acid. Woulf 's apparatus (fig. 321) 
is best adapted for this purpose. The solution has the 
characteristic smell and taste of the gas and all its pro- 
perties. If boiled it loses all its gas, and if kept a short 
time it becomes troubled from precipitation of sulphur : this 
is due to oxygen dissolved in the water. The solution of 
sulphydric acid should therefore be kept in well-stopped bot- 
tles, quite full. This solution is much used in the labora- 
tory. Added to solutions of metallic salts 
it throws down characteristic precipitates, 
offering to the chemist an easy mode of 
distinguishing substances or of separating 
them from one another. The gas passed 
directly into solutions of metals as in fig. 
318, answers the same purpose. Such an 
Fig. 318. apparatus is conveniently kept for use, 

and should be always at hand. 

437. It occurs in nature in many mineral springs, giv- 
ing the water highly valuable medicinal characters. Many 
such springs in this country are much resorted to, as at Sha- 
ron and Avon, N. Y., and the sulphur springs of Virginia. 
At Lake Solfatara, near Home, this gas is given off copi- 
ously with carbonic acid. The disgust at first felt at drink- 
ing these nauseous waters is soon overcome, and those patients 
who take them in large quantity soon observe the gas to 
penetrate their whole system and exude in their perspiration. 
Silver coin, and other silver articles in the pockets of such 
persons, are soon completely blackened by the coating of 
sulphuret of silver formed on their surface. 

Although salutary when taken into the stomach, it is, 
even when present in the air in only a small quantity, a 
deadly poison to the more delicate animals. Numerous 
deaths are also recorded of those who have attempted to work 
in vaults and sewers where it abounds. 

How soluble is it? Will the solution remain unchanged? Why not? 
487. What is its natural history ? How does it affect life ? 





438. When sulphurous 
acid and sulphuretted hy- 
drogen gas are brought 
together in a common 
receiving vessel, mutual 
decomposition ensues, 
and the sulphur of both 
is thrown down, which 
attaches itself to the sides 
of the vessel in a thick 
yellow pellicle. The sul- 
phurous acid is evolved 
in a, (fig. 319,) (310,) Fl * 319 ' 

and sulphydric acic in b, and both are carried to the bottom 

of the middle bottle at a 6. 

Sulphydric acid is formed from 1 volume of hydrogen = 0-0692 

And * volume of sulphuric vapor~£ = i' 1090 

Giving for the theoretical density of the gas 1*1782 

While experiment gives 1*1912 

There is a bisulphydrio acid, HS a , but no further men- 
tion will be made of it. 

439. Selenhydrio and tellurhydric acids are exactly analo- 
gous to the last-named compound, and their general interest 
is so small that we pass them without further notice. 

Compounds of Hydrogen with Class III. 

440. The compounds which hydrogen forms with the nitro- 
gen group are strongly contrasted in chemical and physical 
characters with the remarkable natural family which has 
just engaged our attention. The latter are all acid, and gene- 
rally in an eminent degree. The compounds of hydrogen 
with the nitrogen group are, on the contrary, either neutral 
or strongly basic, forming a series of salts or peculiar com- 
pounds with the hydracids before named. 

The compounds named under this head are — 

Ammonia NH, 

Phosphuretted hydrogen PH S 

We might add in the same connection the hydrogen com- 
pounds of arsenic and antimony, AsH 8 and SbH 3 , sub- 

438. What is the experiment in fig. 319 ? What is the composition of 
this gas? What its theoretical and experimental :&nsity? 439. What 
compounds are used in this section ? Give the formulae. What other 
similar compounds are named ? 




stances quite similar to PH 3 in many of their attributes, 
but convenience refers these to the metallic bodies. 

441. Origin of Ammonia, — Hydrogen and nitrogen do 
not unite in mixture, nor by the aid of heat. A series of 
electrical sparks, as in the case of nitrogen and oxygen, 
(333,) passed through a mixture of hydrogen and nitrogen, 
will produce a limited quantity of ammonia. But it is only 
when these gases come together at the moment of their 
evolution from previous combination, (nascent state, 269,) 
and while, so to speak, they still have the impression of change 
upon them, that they unite with freedom. Ammonia is there- 
fore a constant product in the decomposition of those organic 
substances which contain nitrogen. It is in fact from the 
destructive distillation of horns, hoofs, and other highly ni- 
trogenized forms of animal matter, that the ammonia of 
commerce is in great measure derived. 

This nascent union also occurs without the aid of the 
products of life. A fragment of metallic iron in moist air 
soon contracts a film of oxyd of iron, which, like other porous 
bodies, absorbs the atmospheric gases, while the electrical 
influence of the oxyd of iron with water and metallic iron, 
forming in fact a voltaic circuit, effects a slow decomposition 
of water, whose hydrogen unites in its nascent state with 
atmospheric nitrogen to form ammonia. Thus we reach an 
explanation of the well-known fact, that oxyd of iron often 
contains a notable proportion of ammonia. 

442. Again : Hydrogen is evolved, as all know, by the 
action of dilute sulphuric acid on zinc. Nitric acid effects 
the same end, if of a certain concentration. But if nitric 
acid be added drop by drop to dilute sulphuric acid, while 
hydrogen is being evolved by its action on zinc, the effer- 
vescence from escaping hydrogen is checked, and, if the ad- 
dition of nitric acid is cautiously made, a point is reached 
when the evolution of hydrogen ceases entirely. The zinc 
is still dissolving, but the hydrogen is immediately seized 
as fast as it is evolved, by the nitrogen from the decomposed 
nitric acid, ammonia is formed, and the fluid is found to Con- 
tain a notable quantity of nitrate and sulphate of ammonia. 

441. What is the origin of ammonia ? How do the two gases unite ? 
flow does this happen from the dung of animal matters ? How without 
their aid? 442. How is ammonia formed by the solution of sine? 
Describe the process. 





443. Ammonia was known to the ancients, and bears proof 
of its antiquity in its very name. They obtained sal-ammo- 
niac by burning the dried dung of camels in the desert, whence 
the name, ammonia, from ammos 9 sand, in allusion to the 
desert, which was also called Ammon, one of the names of 
Jupiter. The sal-ammoniac, sulphate of ammonia, and am- 
monia-alum, are found among the products of voicanos. 
Free ammonia is exhaled from the foliage and found in the 
juices of certain plants, in the perspiration of animals, in 
iron rust, and absorbent earths. Rain water also contains a 
small quantity of ammoniacal salts, washed out of the atmo- 
sphere; and the guano so much valued as a manure, is rich 
in various ammoniacal compounds. 

444. Preparation, — Ammonia is prepared by decompos- 
ing sal-ammoniac, by dry lime and heat. For this purpose 
equal parts of dry powdered sal-ammoniac and freshly slaked 
dry lime are well mingled and heated in a glass, or, if the 

Suantity is considerable, in an iron vessel. The lime takes 
tie chlorohydric acid, forming chlorid of calcium, and am- 
monia is given out as a gas. Fig. 320 shows the arrange- 
ment for the purpose. 
The ammonia is col- 
lected over mercury. 
In the laboratory it is 
more convenient to 
employ in the flask e 
strong solution of am- 
monia, which yields 
a large volume of gas 
at a gentle heat. If 
it is required to dry 
the gas, it cannot be 
done by chlorid of 
calcium, which ab- 
sorbs it largely in the 
cold, but dry caustic lime or potassa must be used. 

445. Properties. — The dry gas is colorless, having the 
very pungent smell so well known as that of "hartshorn" 
(because it was procured formerly from the horns of the hart.) 

Fig. 320. 

443. What of the antiquity of ammonia? What natural sources are 
named for it? 444. How is it prepared? Describe the process, ilg. 320. 
445. What are its properties? 





It is, when undiluted, quite irrespirable, and attacks tha 
eyes, month, and nose powerfully. It is strongly alkaline, 
and is often called the volatile alkali. It restores the blue 
of reddened litmus, turns green the blue of cabbage and 
dahlia, and neutralizes the most powerful acids. Its density 
is about half that of air, or 0*597. It does not support 
combustion, but the flame of a candle as it expires in. the 
gas is slightly enlarged, and surrounded with a yellowish 
fringe. A small jet of ammoniacal gas may also be burned 
in an atmosphere of oxygen. With its own volume of oxygen 
it explodes by the electric spark, and produces water and 
free nitrogen. Passed through a tube filled with iron wire, 
and heated to redness, dry ammonia is entirely decomposed; 
yielding for every 200 measures of ammonia, 300 measures 
of hydrogen, and 100 of nitrogen. The metal in the tube 
acts to decompose the ammonia solely by its presence^ (271.) 
At a temperature of 50° it is liquefied with a pressure of 
6i atmospheres, and with the ordinary pressure it is liquid 
at — 40°, producing a white, translucent, crystalline solid, 
heavier than the liquid. 

446. Ammonia is instantly absorbed by water. A frag- 
ment of ice slipped under the lip of an air-jar filled with dry 
ammonia over the mercury cistern is melted at once, and 
the mercury rapidly rises to supply the place of the absorbed 
gas. This forms a weak solution of ammonia, as may be 
shown by its action with reddened litmus. Cold water 
dissolves 500 times its volume of ammonia, all of which is 

Fig. 321. 

How does it act with other bodies? How is it classed? What its 
density? How as respects combustion ? How is it decomposed? What 
Is the product ? 446. How absorbable is it? 





expelled by heat. . This solution is called aqua ammonia. 
It is prepared in a Woulf ' s apparatus b, c, d, (fig. 321,) and 
is evolved from dry lime and sal-ammoniac in a. The tubes 
i dip to the bottom of the water in each bottle, and slight 
pressure may be made by causing the last % to dip into mer- 
cury. The fluid is seen to mouut in o, o, o, indicating tho 
pressure, which of course is greatest in 6. 

447. Solution of ammonia, if saturated in the cold, is 
lighter than water, being sp. gr. 0*870, containing 32} 
parts in 100 of real ammonia. Its odor is overpowering, 
causing suffusion of the eyes and a strong alkaline taste. 
It boils at 130°, and freezes only at — 40°. It saturates 
acids, and forms definite salts. Ammonia is always recog- 
nized by its odor and its restoring the blue of reddened 
litmus, carrying other vegetable blues to green, and browning 
yellow turmeric. Its salts are decomposed by dry lime or 
caustic potassa, evolving the characteristic ammoniacal odor. 
A rod moistened in chlorohydric acid brought 
near a vessel evolving ammonia causes an imme- 
diate cloud of chlorid of ammonium, (fig. 322.) 
It must be preserved in well-stopped bottles in 
a cool place, as the heat of summer or of a warm 
room causes gas enough to be evolved to blow 
out the stopper of the bottle. Fi 8- 322 » 

448. Hydrogen and Phosphorus. — Phosphurettcd Hydro- 
gen. — This gaseous body is conveniently prepared by em- 
ploying quicklime recently slacked, water, and a few sticks 
of phosphorus, in a small retort, (fig. 323,) the ball of which 

Fig. 323. 
is nearly filled with the mixture. A gentle heat generates 

How is aqua ammonia formed ? Describe Woulf 's apparatus. 447. 
What are the properties of the solution ? How are its salts decomposed ? 
448. How is pbosphuretted hydrogen obtained ? 




the gas, which breaks from the surface of 
the water (beneath which the beak of the 
retort dips very slightly) in bubbles, that 
inflame spontaneously as they reach the air, 
rising in beautiful wreaths of smoke, which 
float in concentric, expanding rings. Phos- 
phuret of calcium thrown into a glass of 
water (fig. 324) is instantly decomposed, and 
evolves the spontaneously inflammable gas. 
Fig. 324. Chlorohydric acid evolves from this com- 
pound the variety of this gas which is not spontaneously 

449. Properties. — This gas has a digusting, heavy odor, 
like putrid fish, which is far more annoying than that of 
sulphuretted hydrogen. It is transparent and colorless, has a 
bitter taste, and, if dry, may be kept unchanged either in. the 
light or dark. It loses its spontaneous inflammability by 
standing a time over water, a body being deposited which 
is probably phosphorus, in its red modification. It is 
deadly when breathed. It acts very violently with oxygen 
gas. If bubbles of it are allowed to enter ajar of oxygen, 
each bubble burns with a most brilliant light and a sharp 
explosion. The mixture of even a very small quantity with 
oxygen would be quite hazardous, destroying the vessels. 
Its proporty of spontaneous inflammability is undoubtedly 
owing to a portion of free vapor of phosphorus. In its 
chemical relations phosphuretted hydrogen is nearly neutral, 
but is in some respects a base, as it forms crystalline salts 
with bromohydric and iodehydric acids, which are decom- 
posed again by water. 

There are three phosphurets of hydrogen, P fl H, PH fl , and 
PH 3 . The second of these is a liquid, the third is the sub- 
stance described above. 

Compounds of Hydrogen with the Carbon Group. 

450. Carbon and Hydrogen form a vast number of 
compounds in the organic kingdom, many of which will 
come under our consideration in the organic chemistry. 

449. What are its properties? What is its most remarkable pro- 
perty ? What its constitution ? 450. What compounds of hydrogen and 
earbon are named ? 





There are two gases, marsh gas and olefiant gas, or the 
light and heavy carburetted hydrogens, which are found in 
the inorganic kingdom, although they are derived from the 
destruction of organic bodies. These two compounds we 
will now consider. They are — 

Light carburetted hydrogen gas CH, 

Olefiant, or heavy carburetted hydrogen gas... C.H, 


451. Light Carburetted Hydrogen Gas; Marsh Gas; 
Fire Damp. — This gas occurs abundantly in nature, being 
formed nearly pure by the decomposition of vegetable mat- 
ter under water, (marsh gas.) The bubbles which rise when 
the leaves and mud of a stagnant pool or lake are stirred, 
are light carburetted hydrogen, with some nitrogen and car- 
bonic acid. It may be collected in such situations by means 
of an inverted funnel and bottle, as 
in figure 325. In coal mines it is 
copiously evolved in company with 
heavy carburetted hydrogen and 
carbonic acid, (fire damp.) In the £ 
salt region of Kanawha, it flows =: 
so abundantly from the artesian : 
wells with the salt water, as to fur- 
nish heat enough by its combustion 
for evaporating the salt water. The 
village of Fredonia, in New York, Fi «- 325 \ 

has for many years been illuminated with this gas, derived 
from the saliferous deposits. 

452. Preparation. — Marsh gas is prepared by treating 
equal parts of acetate of soda and solid hydrate of potash 
with one and a half parts of quicklime. The materials are 
ground separately, well mingled, and strongly heated in a 
retort of hard glass protected by a thin sand-bath of sheet- 
iron. The acetic acid C 4 H 4 4 of the acetate is decomposed 
by the potash, which removes from it 2 equivalents of car- 
bonic acid, and marsh gas is evolved, thus : 

Acetic acid C4H4O4 = Carbonic acid, 2 equivalents C» 4 

Marsh gas C»H4 


C%H40 4 

Give their composition. 451. What is marsh gas ? How may it bo 
collected? What other natural sources are named ? 452. How is it pro- 
pared ? Give the reaction. 





The lime preserves the glass of the retort from the action 
of the potash. • 

453. Properties. — Marsh gas is colorless, inodorous, 
slightly absorbed by water, and is respirable when mingled 
with common air. Its weight is about half that of air, or 
'559, and 100 cubic inches weigh 17*41 grains. It burns 
with a yellow flame, giving as the products of combustion 
water and carbonic acid. Mingled with common air, it 
forms an explosive mixture, which collects in large quantities 
in the upper part of the galleries of coal-mines, giving origin 
to fearful explosions and the destruction of many lives of 
miners. Twice its volume of oxygen burns it completely. 
It has never been liquefied. In a tube of porcelain, at full 
redness, it is decomposed, carbon is deposited, and hydrogen 
evolved. With moist chlorine in the sunlight, it forms 
carbonic and chlorohydric acids, but is not affected by it in 
the dark. It is composed in 100 parts, of hydrogen 25, 
vapor of carbon 75 \ or by volume, of 

2 volumes of hydrogen = 0*696X2= 0*1392 

and \ volume of carbon vapor = *829 -~ 2 = 0*4145 

Theoretical density of marsh gas 0*5537 

454. Olcfiant Gas, or heavy Curburetted Hydrogen Gas. 
— This gas was discovered in 1796, by an association of 
Dutch chemists, who gave it the name of defiant, because it 
forms a peculiar oil-like body with chlorine. It is prepared 
by mixing strong alcohol with five or six times its weight 
of oil of vitriol in a capacious retort, and applying heat to 
the mixture. The action is complicated, and cannot be well 
explained at this time. The gaseous products are defiant 
gas, carbonic acid, and sulphurous acid. The alcohol is 

Fig. 326. 

453. What are its properties? What danger arises from it in coal* 
mines? How is it composed by volume ? 454. How is it prepared? 




charred, and at the end of the operation froths up very much. 
The gas can be purified by passing it first through a wash- 
bottle containing a solution of potash, and then through oil 
of vitriol ; the potash removes the acid vapors, and the oil 
of vitriol retains the ether, (fig. 326.) 

455. Properties. — Olefiant gas is a neutral, colorless, 
tasteless gas, nearly inodorous, and having a density of 
0-9784; 100 cubic inches of it weighing 30 57 grains. It 
burns with a most brilliant white light and evolves much 
free carbon. With three volumes of oxygen gas it burns 
completely, with a tremendous detonation, which is too 
severe even for very strong glass vessels. Bub bles of the mix- 
ture may be exploded by a burning paper, as they rise from 
beneath the surface of water. Water and carbonic acid are 
the sole products of this combustion. It is partially decom- 
posed by passing through tubes heated to redness, and much 
carbon is deposited. This effect happens in the iron retorts 
of city gas-works, in which crusts of pure carbon, sometimes 
of great thickness, accumulate from the decomposition of 
the gas. 100 parts of olefiant gas contain 200 hydrogen 
and 100 vapor of carbon. Thus, 

2 volumes of hydrogen weigh 0*1392 14*29 

1 volume of carbon vapor....... 0*8290 85*71 

0*9672 100*00 

Its formula is thence C 4 H 4 , and the experimental density 
(0*9784) is a near approach to the theoretical. 

456. The chlorine compound will be described in the 
organic kingdom. It burns with chlorine, forming chloro- 
hydric acid, and depositing its carbon in a dense cloud. 
Illuminating gas is formed of a union of marsh gas and of 
olefiant with some free hydrogen. The power of illumination 
is derived from the olefiant gas. Ammonia, its sulphuret, 
carbonic acid, tar, and resinous pyrogenic compounds require 
to be removed from coal gas before it is fit for use j and this 
is accomplished by passing it through water, cooling it in con- 
densers, and transmitting it through dry lime purifiers, and 
through dilute solution of sulphate of iron to remove HS 
and C0 9 . 

The other compounds of hydrogen with boron, &c, are 
too little known to require description now. 

455. What its properties ? How much oxygen burns it ? What are 
the products ? How decomposed ? What is its composition ? 456. Whence 
its name ? What is illuminating gas ? 




Combustion, and the Structure of Flame. 

457. Combustion. — This familiar phenomenon is the dis- 
engagement of light and heat which accompanies some cases 
of chemical union. Nearly all our operations being per- 
formed in the atmosphere, the term combustion has come to 
be restricted, in a popular sense, to the union of bodies with 
oxygen, with development of light and heat. Thus, carbon, 
sulphur, phosphorus, &c, are familiar examples of elementary 
combustibles, while oil, tar, coal, wood, &c, are compound 
ones. The products of the combustion of organic bodies 
are all gases or vapors, and are no longer combustible; 
while the products of the combustion of iron, phosphorus, 
potassium &c, are oxyds, bases, or acids, and generally are 
incapable of further change from similar action. Thus, iron 
burns brilliantly in oxygen gas, (277,) forming a com- 
pound, capable of no further change in oxygen. Iron also 
burns in vapor of sulphur, (fig. 232,) but the protosulphuret 
of iron so formed is still capable of burning in oxygen. 
For such reasons as these, bodies were for a long time di- 
vided by chemists into two classes, of combustibles and 
supporters of combustion. This mode of arrangement is 
now for the most part abandoned. It was radically defective 
as a philosophical classification of elements, since it seized 
on a single phenomenon accompanying chemical union, and 
disregarded all those natural analogies which group the ele- 
ments into distinct classes. 

458. In all cases of combustion the action is reciprocal. 
Hydrogen burns in common air ; but if a stream of oxygen 
is thrown into a jar of hydrogen, through a small aperture 
at the top, when the latter is burning, the flame is carried 
down into the body of the jar, and the oxygen will continue 
to burn in the hydrogen, as it issues from the jet. In this 
case the oxygen may be said to be the combustible, and the 
hydrogen the supporter. The simple statement in both 
cases is, that oxygen and hydrogen combine, and combus- 
tion — that is, the disengagement of light and heat — is the 
consequence. (Daniell.) The diamond burns in oxygen gas, 
but the latter is as much altered by the union as the former; 

457. What is combustion ? IIow is the term restricted ? What division 
pf elements was founded on this phenomenon ? 458. What of *he r#- 
flinrocal nature of combustion ? What of light and heat evolved ? 

Digitized by VjOOQ IC 


and wo cannot therefore say whether the oxygen or the 
carbon is the most burnt. Heat and light attend this union : 
but the carbon of the human body is as truly burnt in the 
lungs by the atmospheric oxygen, as is the fuel on our fires. 
The product of this combustion, the carbonic acid, thrown 
out by the lungs at every exhalation, is the same thing as 
the carbonic acid which is discharged at the mouth of a 
furnace. In the case of the animal body, the combustion is 
so slow that no light is evolved, and only that degree of heat 
(98° to 100°) which is essential to vitality. The term 
combustion must have, then, a chemical sense vastly more 
comprehensive than its popular meaning. The rust which 
slowly corrodes and destroys our strongest fixtures of iron, 
and the gradual process of decay which reduces all structures 
of wood to a black mould, are to the chemist as truly cases 
of combustion as those more rapid combinations with oxy- 
gen which are accompanied by the splendid evolution of 
light and heat. 

The heat produced by combustion has received no satis- 
factory explanation. We know that any change of state in 
a body is accompanied by an alteration of temperature. 
When two liquids become solid, we can better understand 
why heat should be produced, (124.) But why the union 
of carbon and oxygen, or of oxygen with hydrogen, to 
form a gas, should evolve such intense heat as to fuse the 
most refractory bodies, is as yet unexplained. 

459. Bodies become visible in the dark at about 1000° 
of heat This fact has been lately confirmed by the re- 
searches of Draper, on the shining by heat of a strip of 
platinum in the dark, when heated by a current of voltaic 
electricity. It is true of all bodies capable of being heated, 
whether solids, or fluids, as melted metals. It is impossible 
by any means to render a gaseous body visibly red. A 
coil of platinum wire suspended in the current of air escap- 
ing from an argand-lamp chimney is at once heated to red- 
ness, while, as every one knows, the hot air itself is entirely 
invisible. Combustible gases heated to a certain point in 
the air, take fire and burn, as when we apply to our gas- 
burner the flame of a match. The color of red-hot bodies de- 
pends on the temperature. Yellow light begins to be evolved 

What chemical extension is given to the term ? Whence the heat 
evolvod in combustion ? 459. At what temperature do bodies become 




at about 1325°, and at 2130° all the colors of the spec 
tram were- observed by Draper in the light viewed by a 
prism as it came from incandescent platinum. A full white 
heat, seen by day-light* is supposed to be at least 3000°. 
The increase of brilliancy in the light from hot bodies is at 
a much higher ratio than the temperature. Thus, the same 
observer found the brilliancy of light at 2590° more than 
thirty-six times as great as it was at 1900°. 

Of Flame. 

460. The structure and nature of flame deserve particu- 
lar notice. If we look attentively at the flame of a 
candle, (fig. 327,) we see that it is formed of several 
distinct parts, wrapped, so to speak, conieally about 
each other. 1st. There is the interior cone a a', form- 
ed entirely of combustible gases, and giving no light. 
2d. The cone efg y which is very brilliant, and where 

| the gaseous contents of the first portion become 

I mingled with atmospheric oxygen ; the hydrogen is 
burned, and the carbon, precipitated in minute parti- 
cles, reflects light powerfully. And 3d. We see the 

I thin outer envelope c d o, where the combustion is 
completed, but where there is much less brilliancy of 

1 illumination than in efg. In the flame of a gas jet A, 
Fig. 327. (fig. 328,) the same parts are recognized, similarly let- 
kc tered, simplified by the absence of the candle-wick, 
whose place is occupied by the ascending stream of gas. 
A section of the candle-flame midway between a a! 
would give us three distinct rings, each marked by its 
own chemical condition. In the centre is the olefiant 
gas of the decomposed fat H, (fig. 329.) The hydro- 
gen of this burns first, forming water, and the carbon is 
raised by the heat of the burning hydrogen to white- 
ness, and fills the space c; while, exte- 
rior it, the thin film o is formed from 
the union of the carbon with oxygen to 
form carbonic acid. Flame may therefore 
^ be considered as a hollow cone of ignited 
uigT328. combustible gas, covering as with a shell Fi S- 329 - 

What was Draper's experiment ? What is the temperature of yellow 
light ? What the brilliancy as compared with temperature ? What is 
noticed in the structure of flame? Describe fig. 327. What are the 
parts of thj flame ? Define flame. 





an interior unignited mass of inflammable gas. This is easily 
demonstrated by introducing a small tube of glass 6, fig. 330, 
into the cone H, by which a portion of the inflammable 
gas is led out and may be burnt at the 
open end of the tube. In like man- 
ner, by bringing a sheet of platinum 
foil over the flame of a large spirit- 
lamp, it will be heated to redness in a 
ring on the outer circle, while the 
centre remains black, showing that the 
interior is comparatively cold. Phos- 
phorus fully ignited in a metallic 
spoon is at once extinguished by im- 
mersion in the interior of a volumin- 
ous flame, like that from alcohol, burn- 
ing in a small capsule. The air is shut Fig. 330. 
out by the screen of flame : the phosphorus, finding no oxy- 
gen, goes out, but may be seen fused in the spoon: bringing 
it again to the air, it is rekindled, and so on. 

461. A high temperature, it will be easily seen, is an 
indispensable condition for a perfect and brilliant combus- 
tion, as the light reflected from the ignited carbon is vastly 
greater at $000° than at 2500°, (459.) A plentiful supply 
of oxygen is of course the antecedent of a perfect combus- 
tion. The candle or lamp becomes smoky whenever these 
conditions are imperfectly fulfilled — as when the 
wick of a candle becomes too long and reduces the 
temperature of the flame below the point of bril- 
liant combustion, supplying at the same time a 
superabundance of material. The candle must 
then be snuffed; or it may be provided with a 
flat plaited wick, as in fig. 331, which bends out- 
ward as it burns, and coming in contact with the 
air, consumes as fast as it protrudes. In all flames 
like that of the candle, when the air has contact 
only on one side, combustion is very imperfect. A 
more rapid and abundant supply of oxygen is the 
object in the construction of the argand and solar 
lamps and all similar contrivances. F>g- 331. 

462. This is accomplished in the argand burner by 

How is it demonstrated by fig. 330 ? What other experiments arc given P 
461. What are the conditions of perfect combustion? Why is a candle 
an imperfect illumination ? What is the principle of the argand burneri ? 






employing a circular wick abed (fig. 
332) arranged between the metallic tabes 
through the centre of which g h a draft of 
air rises, as shown by the central arrows, 
The draft is made more powerful by 
using a glass chimney, contracted at D 
so as to deflect the ascending outer cur- 
rent of air strongly against the flame. 
^ Thus, at the same instant, fresh supplies 
^\ c of oxygen are brought in contact with 
the inner and outer surfaces of flame, 
which still retains the same relation of 
parts as before. The heat of combus- 
tion is enormously increased by these 
means; and with the same amount of 
fuel, a much more brilliant light is pro- 
Fig. 332. duced. In the common double-current 

spirit-lamp, employed in the laboratory for high heats, the 

construction is similar, a metallic 

chimney replacing the glass. A section 

of this lamp is seen in fig. 333. Dr. 

C. T. Jackson has described a modi- 

fication of the double-current spirit- r HKH v 

lamp, in which a blast of air from a H~ D , 

bellows is introduced within the inner 

tube. The arrangement is such »hat 
the blast 

issues in 
a narrow ring, con- 

centric with the wick 

and in close contact Fi ** 333 * 

with it. Properly managed", this lamp 

forms the most powerful lamp-furnace in 

use. The invention in fact ap- r^\ 

plies the principle of the mouth 

blowpipe to the argand lamp. 

In places where gas is used, k 
the gas-lamp, (fig. 334,) fod \ 
Fig. 334. by a flexible pipe and supplied 
with a metallic or mica chimney, leaves nothing 
to be desired for a powerful and economical Fi s- 335# 

Describe fig. 332. Why is the heat increased? What is Jackson*' 
lamp ? What the gas-lamps ? 





beat. A small glass spirit-lamp, with a close cover, (fig. 
335,) to prevent evaporation, is an indispensable convenience 
in even the humblest laboratory. 

463. The Mouth Blowpipe (fig. 336) converts the flame of 
ft common lamp or candle into a powerful furnace. By the 
blast from the jet of the blowpipe, the operator turns the 

Fig. 336. 

flame in a horizontal direction upon the object of experi- 
ment, at the same time that he supplies to the interior cone of 
combustible matter a further quantity of oxygen. The flame 
suffers a remarkable change of appearance as soon as the blast 
strikes it, and the inner blue point b has very different chemi- 
cal effects from the exterior or yellow point c, (fig. 337.) 
Immediately before the 
exterior flame is a stream 
of intensely heated air, 
which is capable of pow- 
erfully oxydizing a body 
held in it, and this point 
is therefore called the 
oxydizing flame. The Fi S* 337 * 

inner or blue point b a is called the reducing flame, and in 
it all metallic oxyds capable of reduction are easily brought 
to the metallic state or to a lower degree of oxydation. Be- 
tween the outer and inner flames is a point of most intense 
heat, where refractory bodies are easily melted. Charcoal 
is generally employed to support bodies before the blow- 
pipe flame, when we would heat them in contact with car- 
bon. Forceps of platinum are used to hold the substance 
when it is to be heated alone. 

If the substance is to be submitted to the action of borax, 

463. What is the principle of the mouth bhw pipe ? What parti 
ore noted in the flame before the jet,fig. 337 ? What is the reducing and 
what the oxydizing flame ? 




or of carbonate of soda, 
or any similar reagent, a 
small platinum wire, bent 
into a loop at one end, 
is used to hold the fused 
globule, as seen in fig. 
! 338. Then, by varying 
Fig. 338. its position in the flame 

as above described, we may submit it successively to the 
reducing agency of carbon vapor, and oxyd of carbon at b f 
to the intense heat of burning carbon at c, or to the power- 
ful oxydizing influence of the current of hot air immediately 
in front of the point c. The art of blowing an unintermit- 
ting stream is soon acquired, by breathing at the same time 
through the mouth and nostrils ; and an experienced opera- 
tor will blow a long time without fatigue. No instrument 
is more useful to the chemist and mineralogist than the 
mouth blowpipe. By its means we may in a few moments 
submit a body to all the changes of heat, or the action of 
reagents, which can be accomplished with a powerful furnace. 

Safety Lamp. 
464. The temperature of flame may be so reduced by 
bringing cold metallic bodies near it as to be extin- 
guished. Davy also observed that a mixture of explosive 
gases, could not be fired through a long narrow orifice like 
a small tube. On these simple facts rests the power of the 
" safety lamp" of Sir Humphry Davy to protect the life of 
the miner. If a narrow coil of copper wire, (fig. 339,) be 
a ^ brought over a candle or lamp so as to 

Ql encircle it, the flame will be extin- 

Fig. 339. guished ; but if the wire be previously 

heated to redness, the flame continues to burn. The same 
effect will be produced by a small metallic tube. A wire held 
in the flame is seen to be surrounded with a ring of non-lu- 
minous matter. If many wires, in the form of a gauze, are 
brought near the flame of a candle, it will be cut off and 
extinguished above ; only a current of heated air and smoko 
will be seen ascending, (fig. 340,) while the flame continues 
to burn beneath, and heats the wire gauze red-hot in a ring, 
marking the limits of the flame. The flame may be relighted 

464. What is the effect of a cold body on flame ? What was Davy's 
observation ? 

Digitized by VjOOQ IC 



above the gauze, and will then burn as usual, as seen in 
fig. 341. Sir Humphry Davy found that a wire gauze 
would in all cases arrest 

progress of flame, 
that a mixture of 


explosive gases could not 
be fired through it. A 
wire gauze is only a series 
of very short square 
tubes, and their power 
to arrest flame comes 

Fig. 340. 

from the fact that they cool the gases below their point of 
ignition. Happily, the heat required to ignite the carbon 
gases is much higher than that which causes the union of 
oxygen and hydrogen. 

465. The fire, damp or explosive atmosphere of coal- 
mines, is a mixture of light and heavy carburetted hydro- 
gen, with many times their volume of common air. These 
gases, being lighter than the air, are found especially in the 
upper part of the galleries of mines, and when the naked 
flame of the miner's lamp meets such an atmosphere, a terrible 
explosion often follows. These explosions in coal-mines b<w\ 
destroyed thousands of those whose duties requir- (f\ 
ed them to submit to the exposure. To avoid these 
lamentable accidents, Davy invented the safety 
lamp. This is only a common lamp surrounded 
by a cage of wire gauze, completely enclosing the 
flame, (fig. 342.) When this lamp is placed in an 
explosive atmosphere, the gas enters the cage, 
enlarges the flame on the wick, and burns quietly, 
the gauze effectually preventing the passage of 
the flame outward. We thus enter the camp of 
the enemy, disarm him, and make him labor for 
us. The miner is not only protected by this in- 
strument, but is rendered conscious of the danger 
by the enlargement of the flame. As long as the 
lamp can burn, it is safe to stay, as an irrespira- 
ble atmosphere would extinguish the flame. The 
powerful blast of wind which sometimes sweeps Fig. 342. 

Explain figs. 340 and 341. What is the application ? What peculiari- 
ty is noticed of the carbohydrogen gases ? 465. What is the fire damp ? 
Where does it chiefly collect? How was Davy's lamp constructed? 
What is its action ? 




through the mines may render the lamp unsafe, by forcing 
the flame against the gauze, until it is heated so hot as to 
inflame the external atmosphere. This accident is prevented 
by the addition of a glass to cover the sides, the air being 
admitted from below through flat gauze discs. 

General Properties of Metals. 

466. The number of the metals is forty-eight, of which 
about half are entirely unknown, except in the laboratory, 
and as the rarest minerals in our cabinets. Of the other 
half, only fourteen or fifteen are familiarly known, or pos- 
sess in a remarkable degree those qualities of ductility, lustre, 
and malleability, which are inseparable from our common 
notions of the metallic character. 

A metal is an opaque body, of a peculiar brilliancy, de- 
scribed as the metallic lustre. It conducts heat and elec- 
tricity, and in electrolysis it goes to the negative pole of the 
voltaic battery, and is therefore an electro-positive body. 
These are the chief characters peculiar to the class. 

Metallic Veins. 

467. In nature, the metals exist commonly in union with 
sulphur, oxygen, and arsenic. A few, as gold, copper, pla- 
tinum, and mercury, are found native, or uncombined, or 
are occasionally alloyed with each other, as native gold nearly 
always contains a portion of silver. When the metals are 
combined with sulphur, or other mineralizing agents, by 
which their proper metallic characters are masked or con- 
cealed, they are called ores. The native metals, gold, cop- 
per, platinum, &c, are not properly denominated ores, being 
obtained in a metallic state from the sands. The discovery 
and extraction of the ores of the metals constitutes the art 
of mining. The separation of the metals from their ores, by 
heat or other means, is a separate branch of chemical art, 
known as metallurgy. Mining demands a minute knowledge 
of thej.mineralogical character of the ores of metals and of 

466. What is the number of metals ? How many are commonly known ? 
What is a metal ? 467. How do the metals exist in nature? What are 
-♦res? What is mining? What is metallurgy? What does mining re« 
/(uire ? 





the earthy minerals with which these are associated; as well 
as the mode of occurrence of mineral veins and ore beds, and 
the mechanical methods adopted for the raising of the ores 
from the earth, their separation from foreign substances, and 
their preparation for market. 

468. The ores of metals are seldom scattered through the 
rocks in a diffused manner, but are usually collected in veins 
or lodes, accompanied by quartz, carbonate of lime, and 
various other minerals, called the vein-stone, or gangue. The 
metal-bearing veins occur more frequently in regions where 
primitive rocks abound, as in granite and its associates. 
Often, however, they extend from these rocks to those which 
rest above them, and are stratified ; showing that the veins 
fill fissures in the earth, occasioned by the cooling of its 
heated mass, and into which the minerals now filling them 
came by injection or infiltration. These fissures usually occur 
together, in a degree of order, the veins being more or less 
parallel, as seen in 
which is an ideal sec- 
tion of a metallic 
deposit, (the veins 
are here seen to 
reach from the gra- 
nite c to the stratifi- 
ed rocks a, a.) Cross 
veins, or courses, 
often intersect in a 
different direction, 
as d } e, &c. , and these 
have usually a mi- Flg ' 343 ' 

neral character entirely distinct, and showing a different age 
and origin. At the intersection of veins there is usually 
an enlargement of the lode, and often a more abundant 
deposit of the metallic ore. It is very rare, if ever, that the 
metallic ore fills the vein entirely. It usually forms small 
threads running through the vein-stone, now expanding, and 
again contracting, as seen in the vertical section of a vein in 
fig. 344, where a, b, c show the rocky gangue surrounding 

468. How are ores found ? What is a vein-stone or gangue? Wnere 
do veins most frequently occur ? Describe fig. 343. Where are veins 
enlarged ? How is the ore usually distributed in mineral veins ? 





the metallic ore d, e y /, g. Often the 
ore dies out entirely, as at o, c, and is 
again renewed farther on. A few 
minerals only are found in beds re- 
gularly stratified between layers of 
other rocks. Some of the ores of 
iron are so found, as well as coal and 
rock-salt. But the mode of origin 
of these last is quite distinct from 
that of the ores of the metals. Fig. 
345 shows the mode of occurrence 

Fig. 344. 

Fig. 345. 

of rock-salt in masses, filling cavities formed probably by 
the solution of minerals previously existing there. 

Physical Properties of Metals. 

469. The physical properties of the metals include their den- 
sity, lustre, color, opacity, malleability,ductility, laminability, 
tenacity, crystallization, fusibility, and conducting power. 
In density, metals present every variety, from potassium 
(•865) and sodium, (-972,) floating on water, to gold (19-26) 
and platina, (21*5,) the heaviest bodies known. In lustre they 
range from the splendor of gold and of burnished silver, to 
the dulness of manganese and of chromium. This property 
often depends on the mechanical condition of the metal ; 
thus, gold and platinum, as thrown down from solution in fine 
powder, are dull yellowish-brown, and black powders, whiqh 
show the lustre and color appropriate to the metals only 
under the burnisher. The color of most of the metals is 
dull white or gray. Silver is nearly pure white ; gold, yel- 

Describe fig. 344. What substances are found in beds ? What is showr. 
in fig. 345 ? 469. What are the physical properties of metals ? What of 
density? What of lustre ? How do mechanical conditions affect lustre ? 




low; and copper and titanium are red. Copper is the basis 
of all colored alloys ; being fused with tin and zinc to form 
bell and gun metal and yellow brass. To determine the 
color of a polished metal accurately, the light must be 
reflected many times from its surface, as may be done by 
placing two polished surfaces of the same metal opposite 
each other, and examining with a prism the light reflected 
at an angle of 90° from them. In this way it is found that 
the proper color of copper is orange-red ; of gold, after ten 
reflections, a beautiful red; of silver, a reddish-white ; of zinc, 
a delicate indigo-blue; of bronze, an intense red; of steel, a 
feeble violet, &c. In looking into a deep vase of polished 
metal, or into a highly polished bronze cannon, or the bore 
of a new steel rifle, these tints of color by reflection are seen. 
Opacity is not absolute in metals, as is proved in the case of 
gold-leaf on glass, through which a beautiful violet-green 
light is seen. This light is found by optical experiments to 
be truly transmitted light, and not a color caused by the mi- 
nute fissures of the gold-leaf. It is worthy of remark that 
this greenish color is complementary to the red, which is 
the reflected color of the gold. 

470. Malleability, or the capability of being beaten by 
blows into thin leaves, is found in the highest perfection in 
gold, and in a good degree in many other metals. Some 
metals are perfectly malleable when cold, as silver, gold, 
lead, and tin ; others are malleable when hot, as iron, plati- 
num, &c, and are not without this property, though in a 
much less degree, even when cold. Some, like zinc, are lami- 
nable at a moderate heat, but brittle above and below 
it; others, like antimony, are brittle at all temperatures 
short of fusion. Gold leaf has been beaten so thin as to 
require 250,000 leaves to equal one inch in thickness, or 1,365 
such leaves would about equal in thickness one leaf of this 
book. Ductility and laminability are properties closely 
allied to malleability. Iron, for instance, unless heated, 
can not be beaten like gold, but it may be drawn into 
fine wire, (ductility,) and plated by rollers into thin sheets, 

What of color ? Enumerate colored metals and alloys ? How are 
metallic colors accurately determined ? What are thus found to bo the 
colors of gold, of copper, of silver, zinc, and bronze ? Is opacity absolute ? 
Why not ? What is proved of the green color of gold ? To what is it 
complementary ? 470. What of malleability, ductility Ac. ? 





Metals are rolled in a machine composed of two equal 
^ssT'v cylinders of iron or steel, seen in section 
i||p!||m in fig. 346. These move in the direction 
SI, : ;^J shown by the arrows. During this process, 
^ ji^l^, the metal becomes more hard and elastic, 
|p|5v owing 10 a rearrangement of its particles. 
^:|p|fj Heated to a redness and slowly cooled, it is 
lilr again softened, and is then said to be annealed. 
Copper is annealed by plunging the red-hot 
Fig. 346. m e tal into water, while the same treatment 
renders steel intensely hard. 

471. The tenacity of metals is compared by using wires 
of the same size of different metals, and ascertaining how 
much weight they will sustain. Iron is the most tenacious, 
and lead the least. The tenacity of wires T J<y of an inch 
in diameter is equal, 

For Iron, to 444 pound*. 

" Copper. 300 « 

" Platinnm 275 " 

" Silver. 171 « 

« Gold 137 " 

For Zinc, to .....100 pounds. 

" Nickel. 07 " 

" Tin 32 " 

" Lead 24 " 

Wires are drawn through smooth conical holes in 
a steel plate, (fig. 347,) each succeeding hole 
being a little less than its predecessor. In 
this way, wires of extreme fineness may be 
I drawn from several of the ductile metals. Dr. 
I Wollaston succeeded, by a. peculiar method, in 
! making a gold wire so small that 530 feet of it 
weighed only one grain ; it was only 5^ ^ of 
an inch in diameter; and a platinum wire 
was made by the same philosopher, of not more 
wwvvw of an inch. Metals passed repeatedly through 
a wireplate, also become stiff and brittle, as in the rolling 

472. Many metals crystallize beautifully, from fusion, when 
slowly cooled, as described for sulphur, (306 ;) bismuth offers 
the most remarkable example of this : others solidify without 
crystallization, or the traces of crystalline structure are seen 
only feebly marked by lines on the surface. Copper, gold, 

Fig. 347. 
than sTsfon 

How are metals rolled? What is annealing? 471. How is tenacity 
shown? Gire examples. How is air formed ? 472. What of crystal- 

Digitized by VjOOQ IC 


•mlver, platina, and some other metals are found crystallised 
* in nature. We can also imitate nature in this respect by the 
Voltaic battery, which enables us to procure many metals in 
perfect crystals. Iron, brass, and other metals often take on 
ft crystalline structure by vibration materially influencing 
their tenacity. The fusion points of several metals were 
given in § 121. 

Many metals are volatile, of which mercury, arsenic, 
tellurium, cadmium, zinc, potassium, and sodium are exam- 
ples, being volatile below a red-heat. Even gold, silver, 
and platinum are raised in vapor by the heat of the voltaic 
focus, (198.) 

Some metals assume a semi-fluid or pasty condition before 
melting, such as platinum and iron, both of which can be 
welded or made to unite without solder, when in this soft 
state ; lead, potassium, and sodium can be welded in the cold, 
as also can mercury, when it is frozen. The conduct- 
ing power of some of the principal metals was given in § 88, 
and their capacity for heat in § 120. 

473. The metals unite with each other to form alloys, 
many of which are familiarly known, as $ copper and i zinc 

' to form brass. Tin and copper form very various alloys, 
according to the proportions employed : 90 copper and 10 
tin form speculum metal, which is as brittle as glass and 
almost white. The alloys of mercury with other metals 
are called amalgams. The fusibility of alloys is often 
greater than that of the constituent metals. . Newton's 
fusible metal, an alloy of 5 parts lead, 3 of tin, and 8 of 
bismuth, is an example of this fact. Lead fuses at 617°, 
bismuth at 509°, and tin at 442°, while Newton's alloy fuses 
at 203°. 

Chemical Relations of the Metals. 

474. The metals, as already stated, are positive electrics. 
Their affinity for oxygen is universal, but various in degree. 
Sodium, potassium, magnesium, and generally the metallic 
bases of the alkalies and earths, have such an avidity for 
oxygen, that they pass at once to the condition of oxyds on 
contact with air. Iron, zinc, copper, &c., are very slowly 

How produced by art? What metals are volatile? What is welding? 
473. What are alloys? What are amalgams? What of Newton i aietal? 
(74. What are the chemical relations of the metals? 




oxydized, and are soon covered by a coat of oxyd, which 
protects the metal from further action. Gold, platinum, 
and silver, on the contrary, resist the action of oxygen per- 
fectly, and are called, from their unalterable nature, noble 

The metallic oxyds may be divided into three classes :— 

1. Basic oxyds, which include the protoxyds generally, 
as potash, soda, lime, and protoxyd of iron. Basic oxyds 
unite readily with acids to form crystallizable salts. Their 
formula is RO. 

2. Acid oxyds, which themselves form salts with powerful 
bases, and rarely, if ever, combine with other acids. Chromic 
acid CrO„ manganic acid MnO„ and other metallic acids 
are examples. Their usual formula is RO a or R0 8 . 

3. Neutral or indifferent oxyds, which, like alumina Aifi^ 
may form salts with either powerful acids, or energetic bases. 
Their formula is R B 8 . 

475. Besides these there are oxyds which unite neither 
with acids nor bases without change, and others which seem 
themselves to be true salts. Of the first the common peroxyd 
of manganese is an example, MnO fl . Heated with sulphuric 
acid it is decomposed, oxygen is evolved, (276,) and sulphate 
of protoxyd of manganese is formed, MnO.S0 8 . Suboxyd 
of lead Pb s O in contact with acids is also transformed into 
metallic lead and protoxyd of lead. 

Of the saline oxyds we have examples in the oxyds of 
manganese, iron, and chromium, whose general formula is 
R 8 4 . In these compounds two oxyds of the same metal 
form, as it were, respectively, acid and base, and we may 
write their formulae RO.R a O a . Magnetic iron is an instance. 

Certain metals form a great number of compounds with 
oxygen, as iron, manganese, and chromium, whose oxyds 
may be represented by the general formulae — 

R the protoxyd, forming a powerful base. 

R*Ot (sesquioxyd,) a feeble base, or neutral, but acting not as an acid. 

R Oa the binoxyd, neither base nor acid, but decomposed by acids. 

R,0 4 a saline compound, whose true constitution is RO.R,0». 

R 0, a metallic acid ; and also 

R*O t a hyper-acid. 

What their affinity for oxygen ? How are the oxyds divided ? What 
are basic ? What acid ? What neutral ? Give their general formulas. 
What other two classes are named ? Give an example of the first. 475. 
Give examples of saline oxyds. 6?lve the general formulae for the oxydf 
of iron, manganese, and chromium. 



SALTS. 285 

Other metals, as arsenic and antimony, have no prot- 
oxyds and form only strong acids with oxygon, by which 
feature they strongly resemble some of the metalloids. 

476. The chlorids, bromids, iodids, sulphurets, &c. of tho 
metals bear a very striking analogy in composition to the 
oxyds of the same metals. So true is this, that knowing 
what oxyds a given metal forms, we can almost certainly 
tell what the composition of its sulphurets, chlorids, &c. will 
be. Thus the oxyds of iron being FeO and FeO a 8 , we find 
that the sulphurets of the same metal are FeS and Fe fl S 8 , 
and the chlorids FeCl and Fe y Cl 3 . It might be inferred 
from this statement that where these metallic bodies unite 
with acids to form salts, there would be the same conformity 
among them that is found among their bases, and such we 
find to be the fact. 


477. A salt, as usually understood, is a compound formed 
by the union of two binary compounds, which stand to each 
other as electro-positive and electro-negative, or as base and 
acid. The bases result always from the union of a metal 
with a metalloid ; the acids usually are derived from the 
union of two metalloids. For example, sulphate of soda 
contains for base, soda (NaO,) formed from the metal sodium 
and the metalloid oxygen, while the sulphuric acid results 
from the union of the two metalloids, oxygen and sulphur. 
The salts of metallic acids, as just explained, (475,) constitute 
an exception, as the metal is present alike in acid and base. 

478. Salts are formed only between members of the same 
class, that is oxygen acids unite with oxygen bases, chlorine 
acids with chlorine bases, sulphids with sulphids, &c., as sul- 
phuric acid with oxyd of iron to form sulphate of protoxyd 
of iron. 

On the other hand, compounds belonging to different series, 
either do not unite at all, or they mutually decompose each 
other. Thus, sulphuric acid cannot unite with sulphuret of 
potassium, a sulphur base, but mutual decomposition occurs, 
sulphydrio acid escapes, and sulphid of potassium is formed. 

What metals have no protoxyds? To what are these affined? 476. 
What analogy have the chlorids, bromids, Ac. of the metals ? 477 What 
is a salt ? How are bases formed ? How the acids ? Give an example. 
What are exceptions ? 478. Between what are salts formed ? How do 
impounds of different classes act together? Give examples. 




Or if chlorohydric acid and oxyd of potassium are brought 
together, chlorid of potassium and water result; thus, 
KO+HCl = HO+KCl. 

479. Neutral salts are formed, when there are as many 
equivalents of acid engaged, as there are of oxygen in the 
base itself. Thus, potash KO has one equivalent of oxygen 
and demands, to form neutral sulphate of potash (KO.S0 8 ) 
one equivalent of sulphuric acid. But one equivalent of SO, 
contains three times as much oxygen as there is in the base, 
and this is true of all the neutral sulphates. The nitrate 
of potash contains dve atoms of oxygen in the acid to one in 
the base, and so on. 

The same is true also of those acids whicn contain no 
oxygen, as the chlorohydric, provided the metallic oxyd dis- 
solves in chlorohydric acid without the evolution of chlorine. 
For example, peroxyd of iron dissolved in chlorohydric acid 
produces water and a perchlorid of iron : 3HC1 and Fe^O, 
giving rise to 3 HO and Fe a Cl 8 . 

480. The binary compounds of chlorine, iodine, &c., with 
many of the metals, particularly those of the alkaline class, 
have in an eminent degree the properties of salts. Among 
them we recognize particularly, the chlorid of sodium, or 
common salt, which is, so to speak, the parent of all salts. 
If the definition of a salt, just given, (477,) be rigidly 
enforced, these bodies cannot be called salts, since, accord- 
ing to that view, a salt is a compound of two binary com- 
pounds, forming a quaternary compound, (245.) To avoid 
this difficulty, two classes of salts have been instituted, the 
first of which includes all those binary compounds which, 
like common salt, have a metallic base in direct union with 
a salt-radical ; and the second includes those salts which, 
like sulphate of soda, are supposed to be constituted of the 
oxyd of the metal and of an oxygen acid. The first have 
'been called the haloid* salts, and the second the ozy- 

479. How are neutral salts formed? What of sulphate of potash ? What 
is the oxygen ratio in the sulphates ? How in case of chlorohydric acid ? 
480. What is said of binary compounds of chlorine, <fec, with metals? 
What of common salt ? What two classes of salts are named ? What is 
meant by salt-radical ? What by haloid salts ? 

* From halt, sea-salty and eidoi, in the likeness o£ 

Digitized by VjOOQiC 

SALTS. 28? 

The term salt-radical includes all the members of tha 
oxygen group except oxygen itself, and also those com- 
pound bodies which, like cyanogen, act the part of ele* 

481. In stating the constitution of sulphuric acid, (320,) 
it will be remembered that the expression S0 4 +H was stated, 
in the view of some chemists, to be equivalent to the com- 
mon formula S0 8 +HO. It is claimed that all the hydrated 
acids are in reality compounds of hydrogen with a similar 
radical, and accordingly nitric acid will be NO fl +H, or cor- 
responding to chlorohydric acid C1H. One principal objec- 
tion to this view is, that these hypothetical radicals have in 
general never been isolated. It is, however, true that those 
acids which are capable of existing dry and in a separate 
state, as sulphuric, (S0 8 ,) phosphoric, (P0 5 ,) nitric, (N0 5? ) 
and carbonic, (CO a ,) are not acids as long as they remain 
dry ; and although they form compounds with dry ammonia, 
that these compounds are not salts. Sir Humphry Davy 
long ago suggested that hydrogen was the real acidifying 
principle in all acids. 

482. If the salt-radical theory is finally adopted, all 
acids must be considered as hydrogen acids, and all salts as 
haloid salts. For example, let us take two common saline 
bodies and present them according to these two views. 

Old view. New view. 

Sulphate of zino .. ZnO 4- SO s Zn 4-S0 4 

Nitrate of soda Na04- N0 5 Na + NO e 

According to the new view, when an acid dissolves a 
metal, there is no necessity for supposing water to be decom- 
posed. The metal takes the place of the hydrogen, and 
the latter is given off in a gaseous form ; or if the oxyd of 
the metal is used, the oxygen and hydrogen unite to form 
water, and no effervescence ensues. 

The apparent simplicity of this view renders it attractive, 
and it has been most warmly supported by Profs. Graham 
and Liebig, while in this country it has found an able op- 
ponent in Dr. Hare. 

481. What is said of the formula of SO t ? What view of acids is suggested ? 
What objection is urged ? What is true of dry S0 3 Ac. Who formerly 
proposed this view ? 482. What will be the constitution of salts in the 
new view ? How does a metal then enter into a salt ? Who support 
and who opposes this view ? 




The nomenclature of the salts has already been explained, 
(251 :) we shall consider the more interesting salt* under 
each metal. \ 

The order in which the metallic bodies are discussed in 
the following pages, is not very different from that usually 
adopted in elementary works. 



Equivalent, 39*2. Symbol, K (Kalium.*) Density, *865. 

483. History. — Potassium was discovered by Sir Humphry 
Davy in 1807 ; at the same time with its congeners, sodium, 
barium, strontium, and calcium. Before that time, the 
alkalies and alkaline earths were looked upon as simple 
elementary bodies, and were so treated in all chemical 
works. Davy found, on passing the electric current from a 
powerful voltaic battery through a cake of moistened potash, 
(oxyd of potassium,) both electrodes being of platinum, that 
violent action followed; oxygen wasevolved with effervescence 
at the positive pole, and bright metallic globules, like mer- 
cury, appeared at the negative pole, accompanied by hydro- 
gen gas. Some of these globules flashed and burned with a 
violet light as they reached the air, while others' remained, 
and were soon covered with a white film that formed on 
their surfaces. These globules were the metal potassium, 
whose discovery constitutes one of the most interesting 
chapters in chemical history. 

Potassium in combination, chiefly as silicate of potash, is 
widely diffused over the globe. It forms a part of all fer- 
tile soils. The chief source from which it is procured is 
the ashes of hard-wooded forest-trees, which take it up from 
soils on which they grow. It is also present in sea-water, 
as chlorid of potassium, and is consequently found in the 
ashes of sea-plants. . 

484. Preparation. — The expensive and troublesome 
method of procuring this metal by galvanism, has been 

What is the nomenclature of the salts ? 483. What is the symbol and 
equivalent of potassium ? When, and by whom, and how was it discovered ? 
How is this metal distributed in nature ? 484. How is potassium prepared ? 





i«_ placed by a much more convenient and productive fur- 
nace operation, founded on the decomposition of potasft at 
a white heat by charcoal. For this purpose carbonate of pot- 
ash is mingled with charcoal. This mixture is best prepared 
by ignited cream of tartar in a covered crucible ; a black 
mass is then obtained commonly known as black flux, con- 
sisting of carbonate of potassa in intimate mixture with 
charcoal derived from the burning of the organic acid. Thig 
mass is finely powdered, and ^ of charcoal in small frag- 
ments is added. The mixture is then placed in an iron 
bottle V (fig. 348) laid horizontally in the furnace M G C. 

The bottle should be about f full, and well protected with a 
refractory lute of 5 parts fine sand and one part fire-clay, 
laid on moist, and well dried in the sun. The cover of the 
furnace M admits the fuel, the draft is regulated by a 
damper, and a temporary front r n closes the side-opening. 
A short iron tube a o connects the retort with a copper con- 
densing chamber ABC containing naphtha, and supported 
on T P S. The heat is gradually raised to the most intense 
whiteness. Decomposition of the carbonate of potash 
ensues, the free carbon takes the oxygen of the carbonate, 
carbonic oxyd (CO) is evolved, and the potassium distils 

Describe fig. 348. 

What is the reaction ? Where does the potassium 




over in metallic globules, which condense in the receiver A. 
This copper vessel is constructed of two parts B C, as seen in 
fig. 349. The upper B enters C, in which the naphtha is 
placed. A vertical partition c d divides B 
m into two chambers, and two openings a b 
opposite each other correspond to the iron 
tube a 0, (fig. 348 :) the partition is also 
pierced in the same line. The outer opening 
b is closed by a cork, and a glass tube g is 
adapted to the opening/, (fig. 348,) by which 
the oxyd of carbon escapes. This condenser 
is kept cold by a constant stream of cold water 
directed on its surface, and the collar m n 
lg * " prevents this from entering the lower vase c. 
The tube a o is very likely to become stopped in the process 
by carbon, and, to avoid this accident, the iron rod, (fig. 350,) 
^^ moistened in naphtha, is 

introduced at b from time 
lg ' * to time to clear it. The 

potassium collects in irregular masses in C, contaminated with 
carbon and other impurities, from which it is freed by a 
second distillation in an iron retort with a little naphtha, by 
which means it is obtained quite pure. 

Naphtha is employed in this process because it contains 
no oxygen, and does not suffer any change from the action 
of the potassium, which is always preserved beneath its sur- 
face and out of contact of air. 

485. Properties. — Potassium, when unoxydized, is a white 
metal with a bluish shade and eminently brilliant. The dull 
masses found in commerce show these metallic characters on 
the fresh-cut surface ; but the proper color and brilliancy dis- 
appear in the air, which instantly tarnishes it. Exposed to 
the air it is gradually converted into a white, brittle mass, 
(potash.) Fused under naphtha, its metallic lustre and color 
are beautifully seen; and a small quantity may thus be forced 
between two test tubes, fitting closely the one within the other, 
so as to exhibit an extended white or bluish-white metallic 
surface, that may be preserved indefinitely under naphtha.. 
At 32° it is brittle and crystalline, at 60° soft and yielding 
to the fingers, between which it may be moulded and welded. 

Describe fig. 349. What precautions are required ? Why is naphtha 
used ? 485. What are its properties ? How is its metallic lustre seon ? 




Heated in air it takes fire and burns with a violet-colored 
flame. At 151° it melts, and below redness it may be dis- 
tilled unchanged in vessels free from oxygen. 

Its density is only -865, being the lightest metal known. 
Consequently it floats on water, which it instantly decom- 
poses; appropriating its oxygen to form oxyd of potassium, 
while the liberated hydrogen burns, with a portion of the 
volatilized metal, with a beautiful violet-colored flame. If this 
experiment is conducted on a vase of water 
reddened by a vegetable color, (fig. 351,) the 
alkali produced changes this color to blue or 
green. The heat produced in this experiment 
is sufficient to fuse the potassium, which as- 
sumes immediately a spherical form and bril- 
liant lustre, and is rapidly driven over the 
surface of the water by the steam and vapors Fi s- 351. 
produced about it, forming altogethel Jne of the most pleas- 
ing and instructive of chemical experiments. If the quan- 
tity of potassium exceeds a few grains, the heat produced 
by its action with the water causes an explosion, projecting 
the burning metal in all directions. An irritating cloud fills 
the air, which is a portion of the alkali (potash) volatilized 
by the heat. 

486. The uses of potassium are confined to the laboratory, 
where, from its energetic affinity for oxygen, it is a powerful 
means of research. By its means we are able to decompose 
the oxyds of aluminum, glucinum, yttrium, thorium, mag- 
nesium, and zirconium, and to obtain the metallic bases of 
these compounds. By it also, as before stated, (379,) we 
obtain boron and silicon from boracic and silicic acids. 

Compounds of Potassium. 

Potassium unites with all the members of the first three 
classes, forming compounds, several of which are of great 
importance in the arts and in pharmacy : of these we can 
describe only a few of the most important. 

487. There are two oxyds of potassium, the protoxyd KO 
and the peroxyd K0 3 . When potassium is heated in a cur- 
rent of dry oxygen it takes fire, burns, and leaves a yellowish 
residue, which is the peroxyd of potassium. This substance 

What is its density ? How does it act on water ? What causes the 
motion? 486* What are its uses ? 487. Name the oxyds of potassium. 




dissolves in water, with the escape of two equivalents of oxy- 
gen, and forms hydrate of potash-solution, KO. HO. Heated 
with twice its own weight of potassium in an atmosphere of 
dry nitrogen, it forms dry oxyd of potassium, thus KO s + 
2K = 3KO. This important compound demands our at- 

488. The oxyd of potassium KO is a powerful base, and 
forms a large class of salts. With water it forms two distinct 
hydrates, KO.HO and K0.5HO, true salts, of which caustic 
potash KO.HO, the monohydrate, is the one chiefly interest- 
ing. This substance is procured usually by decomposing 
pure carbonate of potash, dissolved in 10 parts of water, in 
a clean iron vessel, with half its weight of good quicklime, 
previously slaked and mingled with so much water as to 
form a thin paste, called milk of lime. This is added in small 
portions to the potash solution, while the latter is boiling, a 
short interval allowed between each addition ; all the lime 
being added, the whole is boiled for a few minutes, and then 
is removed from the fire and covered up. The lime displace* 
the carbonic acid, forming carbonate of lime and caustic 
potash. Care is needed to keep the solution dilute, to pre* 
vent the caustic potash formed from decomposing the result- 
ing carbonate of lime. The success of the operation is 
determined by testing a small portion of the clear fluid with 
chlorohydric acid, which should occasion no, or only a feeble, 

The clear dilute solution is drawn off by a siphon, boiled 
away rapidly, (to prevent absorption of CO a from the air,), 
to an oily consistency in a clean iron or silver vessel, and 
finally carried to low redness. The carbonate of potash, if 
any remains, then floats as a scum, being less fusible than 
the caustic, and may be skimmed off. The fused caustic, 
turned out on a plate of copper or iron, hardens into a white 
crystalline cake, which is at once broken up and put in close- 
bottles. To insure its purity from sulphates and chlorids, 
(often present in the original carbonate,) it is dissolved in 
absolute alcohol, which leaves the other salts undissolved. 
The alcoholic solution is decanted, distilled in a retort, and 
evaporated in a silver capsule, fused and cast as before. No* 
degree of heat will expel the equivalent of water which 

How are they obtained ? 488. What of KO ? What is KO.HO ? How 
procured? What the reaction ? How freed from sulphates, lc? 




this hydrate retains. Pure caustic potassa is also obtained 
by decomposing sulphate of potash solution by exactly as 
much oxyd of barium as is required to saturate it. The re- 
action is KO.S0 8 +BaO.HO = BaO.S0 8 +KO.HO. 

489. The hydrate of potash is a white solid, with a crys- 
talline fracture. It has a great avidity for moisture and is 
soluble in half its weight of water. Exposed, it forms a so* 
lotion in the moisture of the atmosphere. It is a most 
powerful base, decomposing by fusion the silicates of nearly 
all metallic oxyds. Cast in cylinders, it forms the caustic 
potassa of surgeons, for which use the mixture of caustic 
and carbonate of lime with potassa is commonly employed in 
pharmacy, under the name of potassa cum cake; and the 
crude potash of commerce, cast in cylinders of a brown color, 
are sold under the name of lapis infernalis. 

The solution of caustic. potash is intensely alkaline, satu- 
rates the most powerful acids, restores the colors of redden- 
ed vegetable blues, and turns many of them green. It has 
an acrid and most disgusting taste, peculiar to alkalies, and, 
when strong, attacks all organic matters, dissolving and dis- 
organizing them, feeling for this reason soapy to the fingers 
on first contact with the solution. With the fats it forms 
soaps, true salts, produced between the fatty acids and the 
alkaline base. It dissolves silica in its soluble form, (382,) 
and even attacks, when concentrated, the glass vessels in 
which it is kept. It absorbs carbonic acid completely, and 
is employed for that purpose in organic analysis. The 
moderately concentrated solution, (sp. gravity 1*2,) as 
procured in the process, (488,) is sufficient for laboratory 
use. Potash is a fatal corrosive poison. 

490. The tests for the presence of potash or its salts are 
ehlorid of platinum, an alcoholic solution of which produces 
a yellow crystalline double salt of potassium and platinum 
in concentrated solutions : perchloric, tartaric, and bydro- 
Suosilicic acids also form sparingly soluble salts with potas- 
sium and its salts. 

491. The chhrid of potassium KC1, is a soluble com- 
pound, crystallizing in cubes. It is formed when potassium 
is heated in chlorine, and when potash or its carbonate is 

489. What are its properties / What are potassa cum calce, and lapis 
infernalis? What of potash solution ? What does it absorb ? 490. What 
are to tests ? 491. What is chlorid of potassium ? 




dissolved in chlorohydric acid. It has a saline bitter taste> 
is deliquescent, and does not possess the antiseptic properties 
of its congener, the chlorid of sodium. 

The bromid of potassium KBr is also a soluble cubical 
salt, possessing the medical properties of bromine. It is pro- 
duced in the mother liquor of the salines, (294,) and has 
been sold fraudulently for the iodid of potassium, which it 
much resembles, but does not replace in medical use. Chlo- 
rine and the stronger acids decompose it with evolution of 

The iodid of 'potassium KI, often called the hydrio- 
date of potashy is a compound of great importance in medi- 
cal practice and in photography. It occurs in cubical crys- 
tals, which are soluble in J parts of water and in 6 parts of 
alcohol of .85. It is obtained when iodine is dissolved in 
potash solution to saturation, and also at the same time iodate 
of potash, (KO.I0 5 .) The iodid is separated by repeated 
crystallization, or if the whole saline mass is ignited, oxygen 
is expelled and only iodid of potassium is left. Its solution 
dissolves iodine largely and acquires thereby a dark color. 
Starch paste, as before stated, is the appropriate test for it. 
The Jiuorid of potassium KP, is also a soluble cubical salt, 
exactly analogous to the foregoing compounds. 

The cyanid of potassium is described in the organic 

492. The sulphur ets of potassium are numerous, five of 
which are described, viz. KS, KS fl , KS a , KS 4 , KS 5 . The 
protosulphuret KS is found in an impure state, when an 
intimate mixture of 2 parts of sulphate of potash and 1 
part of lamp-black are fused together in a crucible. Owing 
to the minute division of its particles with the excess of car- 
bon, it forms a very inflammable mass, which takes fire on 
exposure to air. This has been called a pyrophorus, or 
bearer of fire. The protosulphuret of potassium is also 
formed by saturating a solution of potassa with sulphydrio 
acid, which, evaporated, leaves a white crystalline mass. 
From this salt all the other sulphurets of potassium may 
be formed. 

How different from chlorid of sodium ? What of bromid ? What fraud 
has it served ? What sources has it ? What is iodid of potassium ? How 
obtained? What importance has it? 492. What sulphurets of potas- 
sium are named? How is the protosulphuret formed? What is the 
yyropherus ? 




The pentasulphuret KS 5 is produced most readily by heat- 
ing a strong solution of potassa with an excess of sulphur. 
A large part of the sulphur is dissolved, forming a deep 
yellow liquid which contains pentasulphuret of potassium, 
and hyposulphite of potassa. The pentasulphuret of potas- 
sium in the solid state has the old name of liver of sulphur^ 
and its solution is used in diseases of the skin and as a de- 

493. When potassium is heated in dry ammonia, an olive- 
green compound is formed, (K.NH fl ,) which when heated 
evolves ammonia and leaves a dark gray powder resembling 
graphite, which is a compound of nitrogen and potassium, 
having the formula K fl N. The other compounds of potas- 
sium, with phosphorus, carbon, boron, &c., are comparatively 

Salts of Potash. 

494. The salts of potash are numerous and important. 
We shall, however, mention now only the carbonates, sul- 
phates, nitrate, and chlorate. As it will be altogether im- 
possible to give even the names of all the salts of the metals, 
we must content ourselves with a selection of the most im- 
portant and interesting. 

495. Carbonates of Potash. — There are three carbonates 
of potash, the neutral carbonate KO.CO fl , the sesquicarbonate 
K0.JC0 3 , and the bicarbonate K0.2CO a . 

The neutral carbonate KO.CO fl is procured from the ashes 
of plants, and in an impure form is made on a great scale in 
America, under the names of pot void pearl ashes, which are 
the alkali as obtained from the lixiviation and combustion 
of the ashes of forest-trees. 

The crude carbonate of potash of commerce is contami- 
nated by silica, sulphate of potash, and chlorids of potassium 
and sodium. The latter impurity is frequently added in the 
process of manufacture, either through ignorance or from 
fraudulent motives. The best potash is made by using hot 
water to lixiviate the ashes, in small leach-tubs. The brown 
mass left by evaporating the lixivium to dryness in iron 

How is pentasulphuret of potassium formed? What uses has it? 
493. What is the action of dry ammonia with K ? 494. What salts of 

Ktash are formed ? 495. What carbonates ? How is the neutral car- 
nate obtained ? What are pot and pearl ashes ? What impurities hag 
the crude article? How does "pearlash" differ from "potaahl" 




kettles is the potash of commerce. This is moderately cal- 
cined to hum off the coloring matter, when a spongy mate 
of a fine light blue color is left, which is the pearlash. 

Several samples of American potash examined by Dr. L. 
C. Beck, yielded 73-6, 74-6, 75 and 769 per cent of car- 
bonate and hydrate of potash; from 6 to 15 per cent, of 
chlorids of potassium and sodium ; with from 1 to 15 per 
cent, of insoluble matter, consisting of silica and the oxyde 
of iron and manganese, with lime, alumina, &c., being the 
ingredients derived from the inorganic parts of the plant. 

496. The pure carbonate is obtained by calcining the 
cream of tartar, (acid tartrate of potash,) and dissolving out 
the carbonate from the coaly mass by water. The filtered 
solution is evaporated to dryness in a silver capsule, and the 
salt obtained pure. 

The carbonate of potash has a strong alkaline taste, turns 
blue cabbage or dahlia-paper green, and is somewhat caustic; 
it dissolves in about twice its weight of water, forming a so- 
lution, which is much used in the laboratory. It crystallizes 
with difficulty, and takes up two equivalents (20 per cent.) 
of water in so doing. It is quite insoluble in alcohol. It is 
a very deliquescent salt, and must be kept in well-stopped 
bottles. Its solution acts as a poison if taken in a concen- 
trated form. It usually retains a trace of silica, which is 
soluble in the concentrated solution. 

Bicarbonate of Potash K0.2CO s is formed by passing a 
stream of carbonic acid gas through a cold solution of car- 
bonate of potash. It crystallizes in large and beautiful 
crystals, referable to the right rhombic system. These 
crystals contain 9 per cent, of water and have the 'formula 
K0.2CO fl -|-HO. Four parts of water dissolve it; the solu- 
tion has an alkaline taste and reaction, but is not caustic ; 
by heat it is converted to the simple carbonate, and it loses 
a portion of carbonic acid by solution in hot water. 

497. Alkalimetry. — The value of commercial samples of 
the carbonates of potassa and soda is determined by the 
process of alkalimetry, which consists in ascertaining how 
much dilute sulphuric acid of a standard strength is required 
to neutralize, exactly, a known weight of the sample exa- 

What is the composition of commercial potash ? 496. How is pure car- 
bonate obtained? What are its characters? How is the bicarbonate 
•btained ? What its form and character ? 497. "VYhat is alkalimetry ? 




mined. The strength of the acid is such that 100 
k by measure will exactly saturate 10 parts by weight o! 
pure alkaline carbonate. It is foreign to our present pur- 
pose to give the full details of this process. 

498. Sulphate of Potash, KO.SO ? .— This salt is prepared 
by neutralizing a concentrated solution of potash by strong 
sulphuric acid, added drop by drop. It is also a result of 
many processes in the arts. It fuses at a red heat without 
change. It is an anhydrous, crystallized salt, which decre- 
pitates with heat, and has a density of 2-4. This salt requires 
100 parts of water to dissolve 8-36 parts at 32°, and 0-096 
parts more of the salt dissolve for every degree above that. 
It is one of the hardest of the saline bodies. It is wholly 
insoluble in alcohol. 

Bisidphate of Potash K0.S0 8 -fH0.S0 8 is a result of the 
nitric acid process (334) when a double equivalent of suk 
phurio acid is used. It is properly a double sulphate of 
potassa and water. It is formed also when sulphate of 
potassa is added to its own weight of S0 8 . It fuses at 392° 
without change and without loss of water. A higher heat 
expels one equivalent of sulphuric acid. It is decomposed 
by absolute alcohol, leaving KO.S0 8 . It is dimorphous, 
one of its forms being identical with crystallized sulphur. 
The solution is strongly acid, and acts on bases nearly as 
powerfully as if potash were not present. When this salt is 
exposed to air, beautiful silky crystals, resembling asbestus, 
effloresce upon its surface. These are sesquisulphate of 
potash 2KO.S0 8 +HO.S0 3 . 

499. Nitrate of Potassa; Saltpetre; Nitre; KO.NO s . 
This important salt is a natural product in the hot and dry 
regions of India and South America, being formed by the 
gradual decomposition of animal matters in the soil. It is 
also formed artificially by heaping together beds of old 
mortar and earth with dung and other animal matters, and 
occasionally wetting the mass with fermenting urine. In 
the Mammoth Cave in Kentucky, and other caverns, the 
soil on the floors becomes strongly impregnated with nitrate 
of lime, which is decomposed by wood ashes, and yields 

Give the principle of the process. 498. What is sulphate of KO ? 
Give its properties, Ac. Give the formula for bisulphate of potash. 
What is its proper name ? Give its properties. What is sesquisulphate 
of KO? Hoir produced? 499. What is KO.NO,? How formed and 
found ? How formed artificially ? What the origin of the NO s ? 




nitrate of potassa. In all these cases, the nitre is obtained 
by lixiviating the nitrous earth with water, evaporating and 
crystallizing the solution, redissolving and crystallizing a 
second time, until the salt is obtained pure. Nitre also 
crystallizes from the juices of some plants. 

It appears that the nitre of caverns must come from the 
union of the elements of the atmosphere, under the influence 
of carbonate and nitrate of ammonia, always found to some 
extent in the air. Rain water usually contains a trace of 
nitrate of ammonia, produced, as is supposed, by the union 
of the elements of the air by natural electricity, (§ 331 and 
fig. 252.) 

500. Properties. — Nitre crystallizes in long, six-sided 
prisms, with dihedral summits, derived from the right 
rhombic prism. Its density is 1*94. It is anhydrous, and 
fusible at about 660° : at a higher temperature it is decom- 
posed, yielding oxygen and nitrite of potassa. It is unaltered 
in the air and insoluble in alcohol, but dissolves in about 3 
parts of water at 60°. In hot water it is much more soluble, 
100 parts of water at 206-6° dissolving 236 parts of the salt. 
Its solution has a cooling taste, and is slightly bitter. It 
is an antiseptic, and is used in the brine for preserving 
meats, to give a fine red color to the flesh. 

Nitrate of potassa (as well as nitrate of soda) has been 
much esteemed as a manure. It is employed also to pro- 
cure oxygen, (275,) and the best nitric acid is made from 
it, (334.) 

501. The great quantity of oxygen contained in nitre, 
and the ease with which it parts with it, render it a power- 
ful means of oxydation. Fused on a coal it deflagrates bril- 
liantly. It is the chief constituent of gunpowder, imparting 
oxygen to the carbon and sulphur in that mixture, to form 
with explosive energy those gases which are generated by 
the combustion of the materials. It is also much used in 
all pyrotechnic mixtures, as well as to deflagrate and scorify 
metals. The surface of silver-ware is often scorified by nitre, 
which burns out the alloyed copper, and leaves a surface of 
pure silver. Good gunpowder is composed very nearly of 
1 equivalent of nitre, 3 of carbon, and 1 of sulphur. Thus 

How is it procured from the nitrate of lime ? 500. What are the pro 
perties of nitre ? 501. What renders nitre a valuable reagent? What ii 
an antiseptic ? Of what is nitre the chief constituent ? 




the powder used in war has the following composition in 
different countries : — 

Sulphur 11-9 12-5 11-5 10 9 9-9 

Charcoal. 13-5 12-5 13-5 15... 16 14-4 

Nitre 74-6 75- 75- 75 75 75-7 

Much of the explosive energy of gunpowder depends on 
its granulation ; a fine dust, of the same composition with 
powerful powder, burns with a rapid deflagration, but with- 
out explosion. The constitution of gunpowder is varied 
according to the use for which it is intended. Thus, 20 
sulphur, 18 charcoal, and 62 nitre, are used for blasting- 
powder in mines, and its combustion may be rendered still 
slower by mixing it with several times its bulk of sawdust. 
The effect then is more powerful in moving large masses of 

The gases formed in the combustion of gunpowder are 
carbonic acid and nitrogen, while sulphuret of potassium 
remains as a solid residue. The combustion of a squib, or 
moist gunpowder, gives a much more complicated result; 
nitric oxyd, sulphuretted hydrogen, carbonic acid, carbonic 
oxyd, nitrogen, and other products being formed. 

502. Chlorate of Potash, K0.C10 5 .— This salt is the salt 
already named (275) as the best source of pure oxygen gas. 
It is formed by passing chlorine gas through a strong solution 
of carbonate of potash, chlorate of potash and chlorid of po- 
tassium being formed, the chlorate being easily crystallized 
out by its less solubility. The carbonic acid escapes. The 
reaction is between 6KO.CO a -f 6C1 = 5KC1 + KO.C10 4 

+ 6C( V 

503. Properties. — Chlorate of potash crystallizes in flat, 

pearly tables, referable to the oblique rhombic prism. Water 
at 32° dissolves only 3-3 parts in 100; at 60° only 6 parts, 
while boiling water dissolves nearly 60 parts ; it is therefore 
much more soluble in hot than in cold water. It is insolu- 
ble in alcohol. Its taste is cooling and disagreeable, resem- 
bling nitre. It fuses at 750° ; above that heat, oxygen is 
given off, and chlorid of potassium left behind. It is a most 

What is tho constitution of gunpowder in different countries ? On what 
does its explosive energy depend ? What are the products of its combus- 
tion ? If wet, what are they? How is blasting-powder made more effi- 
cient? 502. What is chlorate of potassa, and how formed? 503. What 
are its properties ? 




energetic oxydizing agent. It forms explosive lpixtures witJl 
nearly all combustible bodies. 

504. With sulphur and charcoal it forms a compound that 
explodes by friction, or by a drop of sulphuric acid, and was. 
formerly much used in the preparation of friction matches. 
With sulphur alone, it detonates powerfully when wrapped 
in a paper and struck by a hammer. With phosphorus its 
reaction is extremely violent ; a deafening explosion follows 
the slightest compression of the ingredients, and burning 
phosphorus is projected in all directions. Its large con- 
sumption in the preparation of matches has rendered it a 
cheap salt. 

Ail attempts to form a gunpowder of chlorate of potash 
have failed, the action of the mixture being so violent as to 
rend asunder the arms employed. A mixture of sugar and 
chlorate of potash is instantly inflamed by a drop of sulphu- 
ric acid, and burns with the violet color which belongs to all 
the salts of potassium. 

The characters of the salts of potash are the same with 
reagents as those of potassa before given, (490.) The salts 
of the alkalies are distinguished from all other metallic salts 
by yielding no precipitate to an alkaline carbonate. All the 
potash salts form with sulphate of alumina a crystalline 
double sulphate of potassa and alumina — common alum — 
crystallizing in octahedrons. 


Equivalent, 23. Symbol, Na. Density, -972. 

505. Sodium was discovered by Davy soon after the dis- 
covery of potassium, and in the same way. It is now pre- 
pared by a process quite similar to that already described 
(484) for potassium ; the carbonate of soda being used in 
place of the carbonate of potassa. 

This metal forms more than 40 parts in 100 of common 
salt, and is also frequent in various combinations in the 
mineral kingdom. The ashes of sea-plants afford crude 

What its solubility? What is its reaction with combustibles? 604. 
Why not fit for gunpowder? What color does it burn with? What are 
the characters of potash salts? What compound do they form with 
Alumina? 505. Give the history and distribution of sodium. How 
procured ? 



SODIUM. 301 

carbonate of soda, in place of the carbonate of potash pro- 
cured from land-plants. 

506. Sodium is a white metal, with a silvery brilliancy, 
and much resembles potassium in its general properties. Its 
color is much whiter than that of potassium, and its dis- 
position to tarnish less. Its density is *972, and it melts at 
194°. At common temperatures it is harder than potas- 
sium, but is easily moulded in the fingers. It does not in- 
flame on cold water, unless in masses of considerable size, 
but moves about rapidly, fused into a brilliant sphere, until 
it is all consumed. It may be alloyed with potassium by 
simple pressure, and is then inflamed on water, or alone on 
hot water, burning with a bright yellow light, characteristic 
of sodium, and strongly contrasted with the violet color of 
the potassium flame. The same color is seen when a piece 
of soda-glass, or any mineral containing soda, is held in the 
flame of the blowpipe ; the flame is instantly tinged yellow. 
Exposed to the air, sodium soon falls to a white powder of 
oxyd of sodium. 

. The compounds of sodium are so similar to those of potas- 
sium that we can pass them with a brief notice. 

The oxyds of sodium and their hydrates are the same in 
composition as those of potassa. 

507. The hydrate of soda, or caustic soda, NaO.HO, 
is procured by decomposing the carbonate by quicklime, in 
the same manner as has already been described for caustic 
potash, (488.) It is a powerful alkaline base, very soluble in 
water, and deliquescent in moist air. It forms a white 
crystalline cake, resembling potassa. It is a corrosive and 
energetic poison. All its salts are soluble, which renders it 
somewhat difficult to detect its presence in solution. 

508. CMor id of Sodium, or Common Salt, NaCl. — This 
familiar and abundant substance is too well known to need 
much description. It is formed when sodium burns in 
chlorine gas, as well as when soda, or its carbonate, is neu- 
tralized by chlorohydric acid. In Poland, Austria, Spain, 
Sicily, and Switzerland, extensive beds of pure rock-salt are 
found, which are regularly mined. Common salt forms 
about 27 of every 1000 parts of sea-water, and in warm 

506. What its properties? What is the color of its flame? What of 
its compounds ? 507. What is NaO.HO ? How procured ? Give its pro- 
perties. What of its salts? 508. What is NaCl? How artificially 
formed ? How found in nature ? 




climates, especially in the West Indies, sea-water is evapo- 
rated in large quantities by the sun's beat, to obtain salt. 
Numerous saline springs are found in New York, Ohio, 
Kentucky, and other places in this country, which afford 
vast quantities of salt by evaporation. The brine springs in 
Onondaga county, New York, are among the most valuable, 
and have been worked since 1789. Their water contains one- 
seventh part of dry salt. The water of the Great Salt Lake, 
in Deseret, contains 200 parts of salt in 1000, or over Hh 
of its weight. This salt is nearly pure. The Dead Sea has 
a still greater concentration, (§ 544.) 

Common salt crystallizes in cubes, which are anhydrous, 
and crackle, or decrepitate, when heated, owing to water 
mechanically entangled in them. Salt forms singular 
hopper-shaped crystals, (fig. 352.) These are produced on 
the surface of the evaporating brine, and 
grow by increase of the outer edges, as 
gravity sinks them constantly, a trifle 
below the surface of the fluid, each ad- 
ditional row of particles being built upon 
Fig. 352. the upper and outer edge of the last. It 

requires 2*7 parts of water for its solution, and it is equally 
soluble in hot and cold water. In pure alcohol it is scarcely 
at all soluble. Its density is 2*557. It fuses at redness, 
and sublimes in vapor at a higher temperature. It is em- 
ployed for this reason to glaze earthenware, since its vapor 
is decomposed by the oxyd of iron of the clay, chlorid of 
iron being driven off, while soda unites with the silica of 
the clay to form the glaze. 

The bromid, iodid, and sulphurets of sodium resemble the 
corresponding compounds of potassium, and the two former 
likewise crystallize in cubes. 

509. Neutral Sulphate of Soda, Glauber's Salt f NaO. 
SO 8 +(10HO). — This familiar salt is found abundantly in 
commerce in large crystals, which contain more than half 
their weight of crystallization water, viz : 

1 eq. anhydrous sulphate of soda 71 44*10 

10 " water 90 55-90 

1 " crystallized sulphate of soda 161 100*00 

How much in sea water ? in salines ? in the Great Salt Lake ? "What 
of its crystallization ? How are the hoppers formed ? How soluble ? 
Its density ? Why used to glaze pottery ? 509. Give the formula fof 
Glauber's salt What is its composition ? 


by Google 



It fuses at a moderate temperature in its own water *nd 
leaves, on heating, anhydrous sulphate of soda. Expo»"l 
to air, the crystals of Glauber's salt efflo- 
resce, and fall to powder, from loss of 822 


s»S ::: 

sai: ssss 



If its solution is heated above 
93°, anhydrous sulphate of soda is 
thrown down. The solubility of sul- 
phate of soda presents very remarkable 
anomalies. Below 32° it is slightly 
soluble. At 32°, 12 parts dissolve in 100 
parts of water : the quantity dissolved 
increases very rapidly with the tempe- 
rature up to 93°, which presents the 
maximum of solubility of the salt, being 
322 parts in 100 of water. Above that 
point the solubility diminishes rapidly 
with each increment of temperature, 
until at 218° it has diminished to 210 12 
parts in 100 of water. The line ABC 320 as 

on the diagram (fig. 353) illustrates Fig. 353. 

the relations of solubility and temperature in this salt at a 
glance. The vertical divisions O to O' register the range of 
temperature from 32° to 218°; the horizontal ones O (Vindi- 
cate the degree of solubility, which reaches 322 parts at 93°. 
The curve of solubility then descends from B to C, when 
210 parts are dissolved at 218°. The cause of this sud- 
den diminution of solubility, is the decomposition of the 
hydrous salt in solution at that heat, and the precipi- 
tation of a portion of anhydrous sulphate of soda. A solu- 
tion of Glauber's salts saturated at boiling heat in a vessel 
capable of being corked while boiling, and suffered to cool, 
will often crystallize completely on withdrawing the cork, 
a change from the fluid to the solid state occasioned by the 
concussion of the air. The same thing happens if a small 
crystal is dropped into a saturated solution of the salt, 

Sulphate of soda is a familiar aperient. In the arts, its 
chief use is in the preparation of carbonate of soda, as will 
be presently described. It is a result, on a large scale, of 

How does it fuse ? How if exposed ? How does it dissolve in water 
it different temperatures ? What is its curve of solubility ? Describe 
the diagram 353. How is its solution in vacuo crystallized ? What is ill 
use in .the arts ? 




the preparation of cblorobydric acid, (426.) The other 
sulphates of soda require no mention at present. The solu- 
tion of sulphate of soda (12 parts) in strong chlorohydrio 
acid (10 parts) produces cold enough to freeze a considerable! 
quantity of water in summer. 

510. Carbonate of Soda, NaO. CO s . — Soda replaces in the 
ashes of sea-plants the potash found in those of land- 
plants. Hence, formerly, the carbonate of soda of com- 
merce was procured, almost exclusively, from the ashes 
of sea-weeds. This salt is now obtained entirely from 
common salt by the process of Leblanc, which will be briefly 
described. This process depends on the fact that when 
sulphate of soda, carbonate of lime, and carbon are heated 
together, carbonate of soda, oxysulphate of lime, and oxyd 
of carbon are the products. The reaction is between 2 eq. 
of sulphate of soda, 3 of carbonate of lime, and 9 of carbon; 
thus, 2(NaO.SO s ) + 3 (CaO.CO s ) + 9C = 2 (NaO.COJ + 
(2CaS.CaO)+10CO. The oxysulphuret of calcium is 
wholly insoluble in water, which takes out from the pulve- 
rized mass only carbonate of soda. This operation is pre- 
pared in a reverberatory furnace constructed like the section 
seen in fig. 354. The parts A and B receive the mingled 

Fig. 354. 

materials, (1000 parts of anhydrous sulphate of soda, 1040 of 
chalk, and 530 of charcoal powder.) The fire on the grate 
F plays upon the charge on the sole of A, and completes 
the chemical reaction which was begun in B, where the 
charge is first placed : a bridge-wall separates the two. The 
workman judges, by the appearance and consistency of a 

What freezing mixture does it form ? 510. Give the formula for car- 
bonate of soda. How was it procured formerly ? Describe Leblano's pro- 
cess? What is the reaction? Describe fig. 354. What gas is formed f 
How is the progress of the operation determined? 



SODIIfM. 305 

portion withdrawn from time to time, of the progress of the 
operation. The oxyd of carbon forms a blue flame over the 
surface, which disappears when the reaction is over. The 
heat following the arrow, next plays upon solution of car- 
bonate of soda in the boiler C, the lixivium of a previous 
charge, and evaporates it to dryness, while at the same 
time the more dilute solution of carbonate is heated in D, 
to be drawn from time to time into C. The steam and pro- 
ducts of combustion escape by the chimney 0. . 

Carbonate of soda crystallizes in great crystals of an ob- 
lique form and containing 10 atoms of water, viz. NaO. 
CO 3 +10HO, equal to 63 parts water in 100 of the salt. 
It fuses in its own water of crystallization. The anhydrous 
carbonate, as it comes from the furnace, is called soda-ash. 

Bicarbonate of soda is procured by exposing soda-ash to 
carbonic acid from fermenting grain, as in distilleries, or by 
passing this acid into solution of carbonate. It is, so to 
speak, a carbonate of soda plus a carbonate of water, or 
Na0.C0 3 +H0.C0 a . It is not a very solute salt : 100 
parts of water take up 8 of bicarbonate. Boiling water 
expels one of the equivalents of carbonic acid. This is 
the salt used in preparing effervescent draughts. 

The sesquicarbonate of soda, Trona, 2NaO.30O 3 +4HO is 
found native in certain lakes in Africa and South America. 
It crystallizes in right rhomboidal prisms, unchanged in air, 
and little soluble in water. / 

511. Nitrate of Soda, Soda Saltpetre, NaO.N0 5 .— This 
salt is found in India and South America, where extensive 
plains are covered by it, as at Tarapaca in Chili, and Iquique 
in Peru. It resembles nitrate of potassa, but cannot be used 
to replace that salt in gunpowder, on account of its strong 
disposition to attract water from the air. It is much em- 
ployed, however, in procuring nitric acid, and also as a fer- 
tilizer in agriculture. It is a white salt, crystallizing in 
rhombs, specific gravity 2-09, very soluable, with .a cooling 
taste, and deflagrates on burning coals with a strong yellow 
light. By carbonate of potassa in solution it is immediately 
transformed into nitrate of potassa and carbonate of soda. 

How is the solution evaporated ? How does the salt crystallize ? How 
much water has it? How is the bicarbonate formed? How soluble ? 
What is the sesquicarbonate. 511. What is the history of nitrate of soda ? 
What does it resemble ? What its use ? How does it act with com- 
bustibles ? 





512 The phosphates of soda correspond to the three eon* 
ditions of phosphoric acid (355) before noticed : they are— 

1. PkosphateofSoda (tnbasw) H0.2NaO.PO s +24HO.— 
The common phosphate of soda of pharmacy is prepared by 
precipitating the acid phosphate of lime (347) with a slight 
excess of carbonate of soda. It crystallizes in oblique 
rhombic prisms, which are efflorescent. The crystals dissolve 
in four parts of cold water, and undergo the aqueous fusion 
when heated. The salt has a pleasant saline taste, and is 
purgative; its solution is alkaline to test-paper. When 
evaporated above 90° it crystallizes in another form, with 
14 instead of 24 atoms of water. 

2. Subphosphate of soda 3NaO.PO s +24HO is obtained 
by adding solution of caustic soda to the preceding salt. 
The crystals are slender six-sided prisms, soluble in 5 parts 
of cold water. It is decomposed by acids, even the carbonic, 
but suffers no change by heat, except the loss of its water of 
crystallization. Its solution is strongly alkaline. The study 
of these salts by Prof. Graham has greatly enlarged our 
views of chemical philosophy. 

3. Bipkosphate* of Soda, or Superphosphate, 2HO.NaO. 
PO s +HO. — This salt may be obtained by adding phos- 
phoric acid to the ordinary phosphate, until it ceases to pre- 
cipitate chlorid of barium, and exposing the concentrated 
solution to cold. The crystals are prismatic, very soluble, 
and have an acid reaction. When strongly heated, the salt 
becomes changed into monobasic phosphate of soda. 

513. Microcosmic salt, or phosphate of soda and am- 
monia, (HO.NH 4 O.NaO.PO s +8HO,) is much used in blow- 
pipe operations as a flux. It is formed by dissolving with a 
gentle heat, 1 part of chlorid of ammonium and 6 or 7 parts 
of phosphate of soda, in 2 of water. Chlorid of sodium is 
formed, and the microcosmic salt crystallizes out in rhombic 
prisms, which lose 8HO by heat. Its fanciful name was 
derived from its supposed virtues in promoting fertility in 
the impotent. 

514. Bibasic Phosphate of Soda, Pyrophosphate of Soda, 
2NaO.PO s +10HO. — Prepared by strongly heating com- 

512. What phosphates are named ? What is the formula of the tribasic? 
Give its properties. What is the subphosphate ? What the superphos- 
phate ? What of Graham's researches ? What is the biphosphate of 
■oda ? 513. What is microcosmic salt ? How formed ? 514. What if 
bibasic phosphate ? Give its formula. 



MTHIUM. 307 

Bton phosphate of soda, dissolving the residue in water, and 
recr ystallizing. The crystals are very hrilliant, permanent 
in the air, and less soluble than the original phosphate : 
their solution is alkaline. A bibasic phosphate, containing 
an equivalent of basic water, has been obtained ; it does not, 
however, crystallize. 

515. Monobasic Phosphate of Soda, Metaphosphate of 
Soda, NaO.PO s . — Obtained by heating either the acid tri- 
basic phosphate, or microcosmic salt. It is a transparent, 
glassy substance, fusible at a dull red-heat, deliquescent, 
and very soluble in water. It refuses to crystallize, and 
dries up in a gum-like mass. 

The tribasic phosphates give a bright yellow precipitate 
with a solution of nitrate of silver, and with molybdate of 
ammonia : the bibasic and monobasic phosphates afford white 
precipitates with the same substances. The salts of the two 
latter classes, fused with excess of carbonate of soda, yield 
the tribasio modification of the acid. 

516. Borax ; Biborate of Soda ; Tincal; Na0.2B0 3 -f 
10HO. — Borax crystallizes in right rhomboidal prisms, 
which are soluble in 15 or 16 parts of water : the solution 
has an alkaline reaction and sweetish alkaline taste. It 
loses its water by heat, and being very fusible, is much used 
as a flux in metallurgic processes and as a blowpipe reagent. 
It is entirely procured from natural sources of boracic acid 
already mentioned, and from the waters of several lakes in 
Thibet, in which it is dissolved. 


Equivalent, 6*5. Symbol, L. 

517. This very rare metal is a constituent of several 
minerals, as spodumene, petalite, lithia-mica : hence its name, 
from lithos, a stone. The electrolysis of the hydrate afforded 
Davy a white oxydizable metal analogous to sodium. Its 
small atomic weight is remarkable. 

The oxyd LO is an alkali, but much less soluble than 

515. What is the monobasic phosphate ? What are the tests for 
tribasic phosphates ? Of the bibasic ? How are the bibasic, Ac, con- 
verted to the tribasic form ? 516. What is borax ? What its source 
and uses ? 517. What is lithium ? What of LO ? What use for its salts ? 




potash and soda. Its sulphate is a beautiful salt, and gives 
a rosy flame to alcohol. The lithia compounds all give this 
tint to the outer flame of the blowpipe. Some of its salts 
&ave been used internally with advantage in cases of urio 
*cid calculus. 

Equivalent, 18. Symbol, NH 4 , (hypothetical.) 

518. Ammonium, NH 4 . — The compound metallic radical 
ol ammonia has never been isolated, although we have reason 
to believe in its existence. When a solution of ammonia, or of 
sal-ammoniac, is electrolyzed, nitrogen escapes at the -f- side 
and hydrogen at the — side, fig. 355 ; 
but if the latter pole is made by using 
a portion of mercury in the bend of the 
tube b, no hydrogen is evolved, but 
the mercury swells up, loses itp fluidity, 
becomes like soft butter, and gradually 
attains many times its original bulk, 
having the lustre and general character of an amalgam. A 
more simple mode of forming this amalgam, consists in 
making a little potassium or sodium combine by heat with 
about 100 times its weight of metallic mercury. This alloy, 
when placed in a strong solution of sal-ammoniac, begins at 
once to increase in volume by the formation of the ammo- 
niacal amalgam, until it has attained very many times its 
original bulk, and has a pasty, butter-like consistence. 

When the alloy of potassium is placed in hydrochloric acid, 
the alkaline metal decomposes the acid, forming chlorid 
of potassium and evolving hydrogen. If we subsitute for 
the acid (chlorid of hydrogen) a solution of chlorid of zino 
ZnCl, a like decomposition ensues; but the zinc, instead of 
being set free like the hydrogen, combines with mercury to 
form an amalgam. The present reaction is precisely similar; 
chlorid of ammonium NH 4 C1 being substituted for the 

518. What is ammonium? Give its history. How obtained more 
simply than by electrolysis? What is the appearance of the amal- 
gam ? What illustration is given from the alloy in HC1 and in ZnCl J 
What is the reaction in the present case ? 




chlorid of zinc: the ammonium which is liberated com- 
bines with the mercury and forms the light pasty amalgam. 
It crystallizes in cubes at 32°, whereas pure mercury is fluid 
even at a temperature of — 39° F. It is evident that it has 
combined with something which has given it new properties. 
This is supposed to be the metallic radical ammonium. The 
spongy mass, as soon as the electric action ceases, rapidly 
suffers decomposition. Ammonia and hydrogen are set free 
in the proportion of 1 to 2, and the mercury regains its 
original state, unaltered. Berzelius and other able chemists 
explain this reaction, on the ground that the ammonia, by 
gaining an additional equivalent of hydrogen, assumes the 
peculiar character of a metal, and unites with mercury, 
forming an amalgam. This hypothetical metal can replace 
potassium and sodium perfectly in combination, and is there- 
fore isomorphous with them. All the salts of ammonia are, 
on this view, derived from this radical, and its union with 
the second class gives us a series of bodies analogous to the 
chlorids, bromids, &c, of the other electro-positive bases. 

Compounds of Ammonium. 

519. Chlorid of Ammonium ; Sal-Ammoniac, NH 4 C1.— 
This salt occurs in nature, sometimes quite pure, as at De- 
ception Island, and in volcanic districts generally. It was 
originally prepared, in Egypt, (443,) by sublimation from 
the soot of the burnt camel's dung. This is ^. ^ 
done in large flasks of glass, (fig. 356,) the sal- ^Cv%$$^>j 
ammoniac collects in the upper part, and the qcP***^^ 
cake is removed by breaking the bottle. It 
is always contaminated by organic matters. 
It is also obtained largely from the ammo- 
niacal waters of the gas-works. It is purified 
by evaporating the crude solutions to dryness, 
after treating them with a slight excess of 
chlorohydric acid to neutralize tho free am- 
monia, and subliming the dry mass in iron Fig. 356. 

What is the product of its decomposition ? What is the explanation 
of Berzelius? How are the ammoniacal salts viewed? 519. What if 
•al- ammoniac ? How prepared ? 





It has a sharp saline taste, corrodes metals powerfully, it 
soluble in three parts of cold water, and crystallizes from its 
solution in octahedrons. The sublimed salt has a fibrous 
texture, and is very tough and difficult to pulverize. 

The formation of this compound is easily shown by using 
the apparatus already figured, (438,) with hydrochloric 
acid in one flask and strong ammonia water in other; the 
commingling of the dry gases, driven over by heat to the 
central bottle, fills it with a white cloud of sal-ammoniac, 
HCl+NHg =3 NH 4 C1. The preparation and properties of 
ammonia have already been explained, (444.) 

520. Sulphydret of Ammonium, (Hydrosulphuret of Am- 
monia,) NHJ3+HS. — This very useful reagent is formed 
by passing a long-continued, slow current of sulphuretted 
hydrogen from the gas-bottle a, (fig. 357,) through the 
bottles d, e, /, g, filled with strong water of ammonia. This 

arrangement is a 
simple form of 
Woulfe's appara- 
tus, (fig. 257.) A 
single bottle of 
ammonia (as d) is 
sufficient for all 
common pur- 
poses. It should 
be kept cold. The 
ammonia absorbs 
p. 357 an enormous quan- 

tity of the gas, and 
the resulting sulphuret, which has the strong odor of the 
gas, is colorless at first, but gradually assumes a yellow 
color. It forms numerous salts with electro-negative sul- 
phurets, being itself a powerful sulphur base. It is an 
invaluable reagent as a precipitant of the metals, and is also 
used in medicine. 

There are several simple sulphurets of ammonium, but they 
are of no particular interest. 

521. Sulphate of Ammonia, or Sulphate of Oxyd of 

What its properties ? How formed artificially ? 520. What is sulphydret 
of ammonium i Describe fig. 357. What is the chemical character of tkU 
body ? What its uses ? 




Ammonium, NH 4 0.S0 8 +H0. — This salt, which is a pow- 
erful fertilizer, is procured in the large way by neutralizing 
the ammoniacal liquor of the gas-works by sulphuric acid : 
or it may be easily obtained pure by neutralizing dilute sul- 
phuric acid with carbonate of ammonia. 

522. There are several carbonates of ammonia. The 
common sal-volatile of the shops, with a pungent smell and 
alkaline reaction, is nearly a sesquicarbonate 2NH 4 0.3CO r 
Exposed to the air, this salt becomes a white inodorous 
powder, which is the bicarbonate. The sesquicarbonate is 
a very valuable salt to the chemist. It forms the basis of 
the smelling-bottles so much in use. The dry white powder 
formed by the contact of dry carbonic acid and ammonia 
in an apparatus like figure 319, is a neutral anhydrous 
carbonate NH 3 .C0 9 , very pungent and volatile, dissolving 
readily in water. 

523. Nitrate of Ammonia, or Nitrate of Oxyd of Am 
monium, NH 4 0.N0 5 +H0. — This salt has already been 
noticed (338) under the description of nitrous oxyd. Its 
crystals resemble nitre, deliquesce in moist air, and dissolve 
in 2 parts of cold water, the solution sinking the thermo- 
meter to zero, (124.) It deflagrates on burning coals like 
nitre, and hence received the old name of nitrum flammens. 

524. All the ammoniacal salts are volatilized by a high 
temperature, and yield the ammoniacal odor by trituration 
with caustic potassa or lime, or by boiling with solutions of 
potash. They are all soluble, and give a sparingly soluble, 
yellow, crystalline precipitate with chlorid of platinum. 

521. What is sulphate of ammonia ? 522. What carbonates are named ? 
What one is formed from the union of the gases ? 523. What is nitrate 
of ammonia? Give its formula. How decomposed by heat? What if 
its frigorifio poiMr? What name had it? 524. What are tests for am- 
moniacal salts' 





525. This class includes barium, strontium, calcium, and 
magnesium, the bases of the alkaline earths, baryta, strontia, 
lime, and magnesia : these are all soluble to some extent in 
water, with an alkaline reaction, but differ very much in the 
solubility and other properties of their various salts. 

Equivalent 68*5. Symbol, Ba. 

526. Barium is a silver-white malleable metal, easily 
oxydized, and melts at a red heat. It was procured by 
Davy by a process similar to that which yielded potassium, 
&c. It is better obtained by passing vapor of potassium over 
baryta (oxyd of barium) heated to redness in an iron tube. 
Mercury dissolves out the reduced metal, and the amalgam 
is then distilled. It is named, from the striking weight of 
its salts, from barus, heavy. 

527. Baryta, or Protoxyd of Barium, BaO. — Baryta is 
best obtained by decomposing the nitrate at a red heat. It 
is a dry, gray powder, which combines with water to form a 
hydrate, slaking with the evolution of great heat and even 
light. Its density is 5 -45. The hydrate dissolves in two 
parts of hot water, or twenty of cold, and crystallizes in flat 
tables. The aqueous solution is a valuable test for carbonic 

Sulphate of baryta, or heavy spar, is found abundantly, as 
an associate of other minerals, in veins ; and from it, or the 
native carbonate of baryta, all the artificial compounds of 
barium are formed. 

528. The peroxyd of barium BaO a is formed by pass- 
ing pure oxygen gas over the oxyd heated to dull redness in 
a porcelain tube. It is chiefly interesting as being the means 
of procuring the peroxyd of hydrogen, (420.) 

525. What are the metals of the alkaline earths ? 526. What is the equi- 
valent of barium ? Give its properties. Whence its name ? 527. What 
is baryta ? How does it act with water? What its density ? 528. How 
is peroxyd of barium formed, and for what used ? 




Chlorid of Barium, BaCl-f-2HO. — This salt occurs in 
white tabular crystals, containing two equivalents of water, 
which are expelled by heat. It dissolves in a little more 
than twice its weight of cold water, and the solution is a 
valuable reagent for detecting the presence of sulphuric acid. 

529. The nitrate of baryta BaO.N0 5 +HO is also a soluble 
white salt, which crystallizes in anhydrous octahedrons, and 
dissolves in eight parts of cold or three parts of hot water. 
Both it and the chlorid are prepared by dissolving the native 
or artificial carbonate in the proper acid. 

Sulphate of baryta, heavy spar, BaO.SO,, is a mineral 
found abundantly in many places in this country, as at 
Cheshire, Connecticut. It crystallizes in tabular modifica- 
tions of the rhombic prism, often very beautiful. It is also 
found massive at Pillar Point, New York. Its specific gra- 
vity (4*3 to 4*7) gives it the name of heavy spar. It is quite 
insoluble in water or acids, and not easily decomposed. When 
strongly heated with charcoal powder, however, it suffers 
decomposition, BaO.S0 8 -f- 4C = BaS -f- 4CO ; carbonic 
oxyd is given off, and the soluble sulphuret of barium may 
be dissolved out from the coaly mass. 

Sulphate of baryta is extensively ground up for a pigment, 
being mixed with white-lead as an adulteration. 

530. Carbonate of Baryta, BaO.CO a , or the witherite of 
mineralogists, is a mineral of some interest, and useful as 
the chief source of the various compounds of baryta. All 
the soluble baryta salts are poisonous, and their presence 
may always be detected by sulphuric acid, or a soluble sul- 
phate, with which they form the insoluble sulphate of baryta. 

The compounds of barium give a peculiar yellow color to 
the flame of the blowpipe, different from the yellow flame 
of soda. 

Equivalent, 44. Symbol, Sr. 

531. Strontium is obtained from its oxyd in the same 
manner as barium, and, like it, is a white metal, oxydized 

Give the characters of the chlorid of barium. For what is it a test? 
529. How is the nitrate of baryta characterized? How is heavy spat 
found in nature ? Give its formula and properties. 530. What is car- 
bonate of baryta ? What character have the soluble salts of baryta ? How 
is their presence detected ? 531. How is strontium obtained, and how 
characterized ? 




easily in the air, and decomposing water at common tempera- 
tures. There are two oxyds, the protoxyd and the peroxyd 
of strontium, similar in properties to the like oxyds of barium. 
The sulphate of strontia (celestine) is a rather abundant 
mineral, and the carbonate (strontianite) is much esteemed 
by mineralogists. They are very similar in properties to 
the sulphate and carbonate of baryta. 

532. The cMorid of strontium SrCl -f- 9HO is a deli- 
quescent salt, soluble in two parts of cold water. It loses 
its water of crystallization by heat. Both it and the nitrate 
of strontia SrO.N0 5 are much employed by pyrotechnists 
in forming the red fire of theatres and fireworks. All th3 
compounds of strontium give a peculiar red tint to the flame 
of the blowpipe, while the barytic salts do not. The salts 
of strontia are not poisonous. 


Equivalent, 20. Symbol, Ca. 

533. Calcium is a yellowish-white metal, obtained like 
barium, and has so strong a disposition to combine with 
oxygen that it is difficult to observe its properties. 

534. Protoxyd of Calcium, Lime, CaO. — This most valu- 
able substance, so well known as quicklime, is procured in 
a state of great purity by heating the stalactites from caverns, 
or the purest statuary marble, for some hours to full redness 
in an open crucible. The carbonic acid and organic coloring 
matter are driven off, and oxyd of calcium (lime) nearly pure 
remains. Pure lime is a white, very infusible, and rather 

hard body, having a density of 3*18. It 
has a great affinity for carbonic acid, taking 
it from the air and falling to powder, (air- 
slaking.) It also combines with water to 
form a hydrate, evolving great heat, (slak- 
ing.) When this operation is performed 
under a glass bell, (fig. 358,) the vapor of 
water at first condensed on the walls of 

__ the jar soon forms a transparent atmosphere 

Fig. 358. of steam, which, when the bell is raised, 

What familiar salts of this mtal are found native ? 532. Describe the 
ehlorid of strontium. What is it used for ? 533. What is calcium, and 
how is it obtained ? Give its equivalent ? 534. What is lime ? IIow 
procured ? What its density ? What is air-slaking ? What slaking bj 
water f 




breaks on the air in a dense cloud of vapor. The heat is 
greatest when the water is about half the weight of lime 
employed. Is sufficiently high often to inflame gunpow- 
der. The hydrate CaO.HO is a dry, bulky powder, soluble 
in 1000 parts of water, to form lime-water. With water 
it forms a milk of lime; a corrosive paste used to re- 
move hair from hides. Lime-water is a valuable reagent 
and antacid ; it has a disagreeable alkaline taste ; blued 
reddened litmus, and absorbs carbonic acid from the air, by 
which it becomes milky from precipitation of carbonate of 
lime soluble in excess of carbonic acid. 

535. Common lime is prepared by heating limestone (car- 
bonate of lime) in large stone furnaces, filled from the top 
with the limestone and fuel ; the fire is kept up constantly, 
by renewed charges of the materials at top, while the pre- 
pared caustic lime is drawn out at the bottom. The carbonic 
acid is much more rapidly expelled when the vapor of water 
and other products of combustion come in contact with the 
heated limestone. Indeed, it is hardly possible by heat alone 
in close vessels to expel the C0 3 , since carbonate of lime is 
fusible under those circumstances without decomposition. 

Mortar acts as a cement by the slow formation of carbon- 
ate of lime, which binds together the grains of sand that 
# make up the greater part of the mixture. The smaller the 
portion of lime used, and the sharper the silicious sand 
employed, the more firm will be the cement at last ; but it 
is then so much more difficult to work, that an excess of 
Kme is usually employed. The presence of oxyd of iron 
and manganese, of alumina, magnesia, silica, and other like 
substances in a limestone, gives the lime prepared from it 
the property of hardening under water, when it is called 
hydravKc lime. 

Lime is much used in improved agriculture, as a manure. 
It acts to decompose vegetable matters, to neutralize acids, 
dissolve silica, and retain carbonic acid. It is always present 
naturally in every fertile soil, and is a constant ingredient in 
the ashes of most plants. 

536. Chlorid of Calcium, CaCl. — The solution of lime, 

What heat is given out in this operation ? Where greatest ? How 
soluble is the hydrate ? 535. How is common lime prepared ? Why is 
vapor of water useful in the process ? How does mortar act as a cement? 
What is hydraulic lime ? 536. What is the chlorid of calcium ? 




or of its carbonate, in hydrochloric acid to saturation, gives 
us this chlorid. It is when fused a white crystalline solid, 
with a great avidity for moisture, and for this reason it is 
used in the desiccation of gases, &c. It is soluble in alcohol, 
with which it forms a definite crystallizable compound. It 
forms a powerful freezing mixture with ice, (124.) 

The sulphurate and phosphurets of calcium have little in- 
terest. The phosphuret being decomposed by water, is an 
available source of the spontaneously inflammable phosphu- 
retted hydrogen, (fig. 326.) 

537. Sulphate of Lime — Gypsum — Selenite, CaO.SO r 
—This salt, in the form of hydrate CaO.S0 8 +2HO, is 
abundant in nature, and is much used in agriculture as a 
manure, being ground to powder; and, after expelling the 
water by heat, as a material for stucco and plaster casts- 
It is then commonly known as " plaster of Paris." The varie- 
gated and fine white varieties are called alabaster. When 
crystallized in transparent flexible plates, it is called selenite. 
I These crystals are sometimes compound in 
( such a manner as to present an arrow-head 
form, like fig. 359. Such crystals are called 
hemitropes. Anhydrous gypsum CaO.S0 3 also 
is found native, and is known by the minera- 
logical name of anhydrite. 

Gypsum is frequently associated with rock- 
salt It is soluble in about 500 parts of water, 
and is present in most natural waters. By 
a heat of 250° to 270° it loses its water of 
composition: when the anhydrous powder is 
moistened, the lost water is regained, and it 
becomes solid ) but if heated, even to 330°, it 
Fig. 359. no j on g er re g a i ns its water of composition. It 
fuses at a red heat to a crystalline anhydrous mass. This 
power of resolidification, when mixed with water, gives 
gypsum its value in copying works of art, and in forming 
Btucco ornaments. By using solution of common alum in 
place of water, gypsum becomes very hard, and is thus 
treated for producing pavements. 

For what is it used ? What is the phosphuret of calcium used for? 
537. Give the common names of sulphate of lime. For what is it used f 
Give its properties. What is fig. 359 ? How is gypsum hardened ? Om 
what docs its use in stucco depend ? What is anhydrite ? 




538. Fluorid of Calcium, Fluor-spar, CaF. — This is a 
rather abundant mineral, being found beautifully crystallized, 
of various colors, in the cube and its modifications. It is the 
principal source from which we obtain the fluohydric acid 
(433) by decomposition with sulphuric acid. It often phos- 
phoresces very beautifully with heat, emitting a green, 
yellow, or purple light, at a temperature below redness. 

539. Phosphates of Lime. — There are several phosphates 
of lime corresponding to the several phosphoric acids, (355.) 
The earth of bones is a tribasic phosphate of lime, and the 
mineral known as apatite is also a phosphate of lime. The 
phosphates of lime are insoluble in water, but dissolve in 
dilute acids. All cereal grains, and many other vegetables, 
contain phosphate of lime in their ashes, and this salt is 
therefore an indispensable ingredient of all fertile soils, and 
the form in which phosphorus is introduced into the animal 

540. Carbonate of Lime — Marble — Calcareous Spar, 
CaO.CCX,. — This is one of the most abundant minerals of 
the earth, forming in limestone vast mountains and wide- 
spread geological deposites. It oc- 
curs most superbly crystallized in 
rhombohedral forms, which consti- 
tute brilliant ornaments in mineralo- 
gical collections. The transparent 
double refracting Iceland spar, (fig. 
860,) and the dimorphous form, 
arragonite, are examples of this salt. Fig. 360. 

It is soluble in dilute acids, with escape of carbonio acid, and 
is also decomposed by heat, leaving quicklime. 

Water aided by carbonic acid, and perhaps by the organic 
acids of the soil also, dissolves carbonate of lime, and again 
deposits it in stalactites and stalagmites, on exposure to the 
air. These phenomena are beautifully seen in Mammoth 
Cave, Schoharie Cave, and many similar situations. The 
stalactites depend from the roof, growing by the deposit of 
freshly precipitated portions of carbonate of lime on their 

538. What is fluor-spar ? How is it found ? For what used ? What 
beautiful property has it ? 539. What phosphates of lime are known ? 
In what do we find phosphate of lime ? How does phosphorus enter the 
system ? 540. What is the formula of carbonate of lime ? What other 
names has it ? What is formed from it ? What optical property has it? 
How does water dissolve it ? What are stalactites and stalagmites ? 




surfaces, which are kept moist by the trickling of water con* 
taining the salt in solution. The water which falls to the 
floor from the point of each stalactite slowly builds up a coni- 
cal mass called a stalagmite, and when these meet they form 
a column. All these stages are well shown in fig. 361, 

Fig. 361. 

from Regnault. Before these fairy-like creations of nature's 
architecture are darkened by torches, their beauty is en- 

541. Hypochlorite of Limey CaO.CIO, Bleaching-Pow- 
der. — This valuable compound is formed^, when chlorine gas 
is gradually admitted to hydrate of lime slightly moist and 
kept cool. The chlorine is absorbed largely, and the bleach 
ing-powder of the arts is formed. Bleaching- powders con- 
tain a mixture of hypochlorite of lime, chlorid of calcium, 
and hydrate of lime. It is a soft white powder, easily soluble 
in about 10 parts of water, giving a highly alkaline solution, 
which bleaches feebly. It is employed by dipping the 
goods in the weak solution, and then in very dilute acid 
water. The chlorine is thus evolved and does its work. 
Several repetitions are needed to complete the process, and 
the acid is washed out with care. This compound emits a 
strong smell, which is similar to chlorine, but is due ta 

Describe their formation as in fig. 361. What is bleaching-powder ? 
How formed ? How employed ? 




hypochlorous acid ; it is very useful for disinfecting offen- 
sive apartments, and its energy is increased by the addition 
of a little acid water. The disinfecting liquid of Labarraque 
is a compound of chlorine with soda, similar in composition 
to solution of bleaching-powder. 

The best bleaching-powders contain 39 parts of available 
chlorine, and 2 parts, in combination, as chlorid of calcium. 
If one equivalent of each ingredient were present they 
would be in the proportion of 48 -57 chlorine and 51*43 parts 
hydrate of lime. Ordinary bleaching-powders contain only 
about 30 per cent, of chlorine. The mode of determining 
the amount of chlorine present is called chlorimetry, and 
is based on the quantity of sulphate of indigo which is 
decolorized by a standard solution of chlorine. The salts 
of lime are not precipitated by ammonia, but form an entirely 
insoluble oxalate, with oxalic acid or oxalate of ammonia. 


Equivalent, 12*2. Symbol, Mg. 

642. Magnesium is obtained by decomposing the chlorid 
of that metal heated to redness in a glass tube, by passing 
over it the vapor of potassium or sodium. Chlorid of po- 
tassium or sodium is formed, and the metallic magnesium 
is separated by dissolving out the soluble chlorid. 

It is a white metal, malleable and brilliant. It fuses 
with a red heat, and if heated to redness in the air, burns 
with a brilliant light, producing oxyd of magnesium. It 
does not tarnish in dry air, and does not decompose water 
even at 212°, but dissolves in acids with escape of hydrogen. 

543. Oxyd of Magnesium, Calcined Magnesia, MgO. 
This substance is left when the carbonate of magnesia is 
heated to redness. It is a white, very light, earthy powder, 
insoluble in water, but readily soluble in weak acids. It 
occurs in nature crystallized in regular octahedrons, form- 
ing the mineral periclase. It is much used in medicine as 
a mild and efficient aperient. The hydrate of magnesia 

What is Labarraque's liquor ? What is the composition of bleaching, 
powder ? What is chlorimetry ? What precipitates the salts of lime ? 
542. Give the equivalent and preparation of magnesium. What are its 
properties ? 543. What is the oxyd of magnesium ? How is it used 1 
How found in nature ? 




MgO.HO is formed wnen magnesia is precipitated from its 
solutions by an alkali. Heat expels the equivalent of water, 
leaving calcined magnesia. The hydrate is found beau- 
tifully crystallized in thin pearly plates at Hoboken, New 

644. Chlorid of Magnesium, MgCl. — This chlorid is best 
prepared by neutralizing equal portions of chlorohydric acid, 
on 3 with magnesia and the other with ammonia, mixing the 
two portions and evaporating to dryness. The dry mass 5s 
heated in a covered crucible as long as sal-ammoniac is given 
off, when pure chlorid of magnesium is left. It is a very deli- 
quescent salt, and supplies the means of procuring metallic 
magnesium. When magnesia is dissolved in hydrochloric 
acid, a hydrated chlorid of magnesium results. By heat the 
water is expelled, carrying with it chlorohydric acid, and 
leaving pure magnesia behind. The bittern of salt springs 
is chlorid of magnesium ; it exists in sea-water, and is the 
largest ingredient in the waters of the Dead Sea. The iodid 
and bromid of magnesium are also soluble salts, but the 
fluorid is insoluble. 

545. Sulphate of Magnesia, Epsom Salts, MgO.S0 8 -|- 
7HO. — This well-known salt is easily formed by dissolving 
magnesia, or its carbonate, in sulphuric acid. It is also 
found native at Corydon, Illinois. In the waters of Epsom 
Spa, in England, and in numerous mineral waters, it is a 
large constituent. It is made on a large scale by dissolving 
serpentine rock in strong sulphuric acid. It is very soluble, 
and, like all the soluble salts of magnesia, has a peculiar 
bitter taste. 

546. The carbonate of magnesia, magnesite, MgO.COa, 
is found native in magnesian rocks, and is formed artificially 
by decomposing any of the soluble salts of magnesia by an 
alkaline carbonate, giving the magnesia alba of pharmacy. 
It is insoluble in water; but a solution of carbonic acid 
dissolves it, and forms the celebrated Murray* s solution of 
magnesia. It is decomposed by contact of air, carbonic acid 
escapes, and carbonate of magnesia is thrown down. The 
double carbonate of magnesia and lime is found as an ex- 

What is calcined magnesia? 544. How is the chlorid of magnesium 
prepared? Describe it. When magnesia is dissolved in chlorohydric 
acid, what happens ? 545. What is the composition of sulphate of mag- 
nesia? How is it made in the large way? In what waters is it found? 
146. What is carbonate of magnesia ? What is Murray's solution ? 




tensive rock formation, called dolomite, and when crystal 
iized, pearl spar. 

Phosphate of soda with ammonia throws down a crys 
talline insoluble salt from magnesian solutions, which is 
the double phosphate of magnesia and ammonia. This is 
the most ready mode of testing for the presence of magnesia. 

547. Magnesia occurs abundantly in nature as a con- 
stituent of many minerals, as well as in the form of hydrate 
and carbonate. The silicates of magnesia form a very im* 
portant class of minerals, of which talc, soap-stone, pyroxene, 
hornblende, serpentine, &c., are examples. Magnesia is also 
found in the ashes of most plants, in union with phosphoric 


ALUMINUM. Al. = 1 3 -69. 

548. Aluminum is best obtained, like magnesium, by the 
action of sodium or potassium on its chlorid. It. is a gray 
powder, not easily melted, has a metallic lustre, and burns, 
when heated in the air, with a bright light, forming alumina. 

549. Alumina; Sesquioxyd of Aluminum ; Corundum^ 
Al a 8 . — Pure alumina is found crystallized in those precious 
gems, the oriental ruby and sapphire, which are next in 
hardness and value to the diamond. Emery (cornudum) is 
also nearly pure alumina. Alumina is an abundant ingre- 
dient in many other minerals, and forms a large part of many 
slaty rocks, from whose decomposition clays are produced. 

Pure alumina is a fine white powder, not rough and gritty 
like silica. Its density is 4*154. It is infusible except 
under the oxyhydrogen blowpipe. After ignition it is al- 
most or entirely insoluble. 

Hydrate of alumina Al fl O a +3HO exists in the minerals 
diaspore and gibbsite. Alumina is precipitated as a hydrate 
from solution, by either potash, soda, or ammonia, and their 
carbonates; an excess of the first two will redissolve the 
precipitate. The hydrate is very bulky, and shrinks very 

What test have we for magnesia ? 547. How does magnesia occur in 
feature ? Mention some of its silicates. 548. How is aluminum obtained? 
What are its properties and density ? 549. What is the formula of alu- 
mina ? In what is it found pure ? How aro the hydrous and anhydroua 
alumina distinguished ? What precipitates and what redisaolyea it ? 




much on drying. Hydrosulphuret of ammonium throws 
down alumina. The anhydrous alumina is almost insoluble 
in acids, while the hydrate is readily dissolved, forming sails 
of a peculiar astringent taste, familiarly known in common 

The ehlorid of aluminum has no particular interest except 
as a means of procuring the metal. 

Aluminate of potassa KO. Al s O s is formed when a solution 
of alumina in potassa is gently evaporated : it appears in 
crystalline grains. IJaryta and magnesia afford similar 
examples. Spinel, a mineral species, is an aluminate of 
magnesia MgO.Al s 3 . These are instances of the double 
function which alumina possesses of acting the part both of 
acid and base, (474, 3.) 

550. Sulphate of Alumina, Al a 8 .3S0 8 +18HO.— This 
salt is prepared by saturating dilute sulphuric acid with 
alumina : it has a sweetish astringent taste, is soluble in 2 
parts of water, and crystallizes in thin plates. 

Hums. — Sulphate of alumina forms, with potash, soda, 
and ammonia, double salts of much interest, called alums. 
They are all soluble salts, with a sweetish astringent taste, 
and crystallize in the regular system, or first class, (44,) 
usually as modified octahedrons, which have uniformly 24 
equivalents of water of crystallization. Common potash- 
alum has the formula Al a O a .3S0 8 +KO.SOg+24HO, (256;) 
it dissolves in 18 parts of cold water, and the solution has 
an acid reaction. The water of crystallization of the alums 
is expelled by heat : the salt first suffers watery 
fusion, and then swells up into a light porous 
mass, many times the volume of the salt em- 
ployed, and protruding beyond the vessel 
employed, as in fig. 362. This is called burnt- 
alum. All the basic sesquioxyds isomorphous 
with alumina may replace it in the constitu- 
tion of an alum. 

Alum and acetate of alumina are largely 
1 employed in the arts of dyeing and tanning. 
Fig. 362. Alumina combines with coloring matters, and 
seems to form a bond of union between the fibre of the cloth 

What salts does it form? What is aluminate of potassa? What if 
spinel ? Give the formula of alum. 550. What is burnt alum ? What 
is the use of alums ? 




and the color. In this it is said to act the part of a mor- 
dant. When alum is added to the solution of a coloring 
^matter, and the alumina is then precipitated with an alkali, 
all the coloring matter is thrown down with it, and forma 
what is called lake. The common lake used in water-color- 
ing is derived from madder treated in this way. Carmine 
is a lake made from cochineal. 

551. Silicates of Alumina. — This is the most extensive 
and important class of the aluminous salts, and comprises a 
great number of interesting minerals. Feldspar, A1 3 3 # 
SSiOg-f-KO.SiOg, which is one of the chief components of 
granite and granitic rocks, is of this class, and has the com 
position of an anhydrous alum, the sulphuric acid being 
replaced by the silicic. Albite is a salt having soda in place 
of the potash in feldspar, while spodumene and petalite are 
similar compounds, with a portion of the soda replaced by 
Uthia. Kyanite and andalusite are simple basic silicates 
of alumina. Many other similarly constituted compounds 
are found among minerals, some of which are hydrous and 
others anhydrous, and varied by frequent substitution of 
peroxyd of iron, manganese, or other isomorphous bases, 
for the alumina. 

Plants do not take up alumina, and it is not yet proved 
that their ashes ever contain it. Its value in the soil seems 
to be in retaining moisture, ammonia, and carbonic acid, and 
in giving firmness to the other incoherent components of the 
soil. The decomposition of these silicates gives origin to 
olay, whose peculiar qualities derived from the alumina fit 
it for the purpose of the potter. 

This is the place to say a few words upon the two import- 
ant arts of glass-blowing and pottery. 

Manufacture of Glass. 

552. Silicates of Soda. — Both soda and potash unite by 
fusion with silicic acid to form silicates of variable compo- 
sition. If 3 parts of the alkali are used to 1 of the silica, 
tho glass is soluble in water, but whatever may bo the pro- 

What is a mordant ? What a lake ? 551. What is the most important 
class of alumina compounds ? What is the formula of feldspar ? What 
silicates are named? What is the function of alumina in soils? What 
aqe clays ? 552. How do the alkalies unite with silica. What is the cha* 
racier of the compounds so obtained ? 




portions used, tbe resulting silicate is always an uti crystal- 
line, homogeneous, transparent mass. The "soluble glass" 
formed by fusing together 8 parts of carbonate of soda (or 
10 of carbonate of potash) with 15 parts of pure sand and 
1 of charcoal, is insoluble in cold, but dissolves in 4 or 5 
parts of hot water, forming a sort of Tarnish, which may be 
applied to wood or manufactured stuffs, which are to a good 
degree protected from it by the action of fire. 

553. Glass is a variable compound of the silicates of! 
potash, soda, lime, and alumina, with oxyds of lead and 
iron, fused together by a very high and long-continued heat, 
in proportions suited to the object for which the glass is to 
be used. The relation between the oxygen in the base and 
that in the silica determines the degree of fusibility of the 
glass : thus, the greater the proportion of silica the less the 
fusibility of glass. The principal varieties of glass are 
these, viz : 

Window glass, a silicate of soda and lime, which re- 
quires an intense heat for its fusion, and forms a very 
hard and brilliant glass. Plate glass, such as is used for 
mirrors, crown glass employed for glazing, and the beauti- 
ful Bohemian glass, are all silicates of potash and lime. 

Crystal glass is formed by fusing together 120 parts of 
fine sand, 40 of purified potash, 36 of litharge or minium, 
(oxyd of lead,) and 12 of nitre. This forms a very fusible 
glass easily worked, and so soft as to be cut and polished 
with comparative ease. The oxyd of lead greatly increases 
its brilliancy. 

Green bottle-glass is usually a silicate of lime and alumina! 
with oxyds of iron and manganese, and potash or soda. It 
is formed of the cheapest refuse of the soap-boiler's waste, 
and lime which has been used to make caustic potash or 

554. The processes of the glass-house are all exceedingly 
interesting and instructive — the tools few and simple — the 
results dependent on the adroit manipulations of the work- 
man. The materials are fused in clay pots, of which seve- 
ral are heated in one circular reverberatory furnace, their 

What is soluble glass ? 553. What is glass ? What determines th# 
fusibility of glass ? What sorts are named ? What is the composition 
of window and plate ? What of crystal ? What of green bottle-glass? 
654. How are the materials fused ? 





mouths outward. Fig. 363 shows a section 
of one of them. After two days and nights, 
tiie metal, or fused glass, is brought to a 
homogeneous condition and the consistence of 
honey. The chief instrument of the glass- 
blower is his punta rod, which is simply an 
iron tube a b, fig 364, open at both ends and 
covered by a wooden collar c d to protect the Fi 363 
hands from the heat. This rod is thrust into 
the pot of molten glass while it is turned in the hand, a 

portion of the fluid j g d * 

glass adheres to it, the •■■ ^S5a™i^Hi*™=^^^=^ 
rod is withdrawn, and Fi * 364 ' 

if enough has not adhered to meet the wants of the work- 
man, he takes up a second portion. This he first fashions 
into a cylindrical form upon a 
slab of iron, rolling the rod over 
and over in his hand, (fig. 365.) 
Suppose it is required to make 
a glass tube, such as is so much 
used in the laboratory. He ap- Fig ' m 

plies his mouth to the end of the punta-rod and blows. 
The cylinder of glass is inflated, find assumes M ^% 
a pear shape, as in fig. 366. An assistant now ' ^vJP. 
applies his tube, containing also a small Fi S« 366 - 
portion of hot glass, to the opposite extremity of the first 
mass, (fig. 367,) and drawing against the other, the ellipti- 

Fig. 367. Fig. 368. 

oal mass is elongated and assumes the form seen in fig. 368. 
The two workmen now walk rapidly away from each other in 
opposite directions, drawing their tubes in the same line, 
giving the ductile glass the form of a tube, as seen in fig. 
369. A few inches from each punta-tube the glass beconfes 

Fig. 3G0. 
of a uniform size, the small cavity originally blown in the 

What are the instruments used? How is a glass tube formed? 
Irate the process from figs. 363-369. What is pressed glass ? 





mass (fig. 366) is elongated to a smooth cylindrical bore, ainl 
however small the glass tube may be drawn out, this bort 
always remains circular and entire through its whole length, 
To fashion a bottle, the operation is commenced in the same 
manner, but the adroitness of the workman enables him to 
elongate it by centrifugal force, wheeling the molten mass 
over his head while he inflates it; a«d the bottom is drawn in 
by revolving the rod rapidly on a crotch while he applies the 
surface of an iron instrument to the revolving flexible glass 
to fashion it at his will. Most of the cheap glass vessels now 
manufactured are formed by blowing the glass in a metallic 
mould opening in two parts. This is called pressed glass. 
In the laboratory a flat lamp, like fig. 370, fed with tallow, 

is employed to fashion tabes 
into the various forms re- 
quired for the construction 
of the apparatus. The flame 
is driven by a bellows under 
the table worked by the foot 
F 370 With a little practice, the 

lff * ' operator soon acquires suf- 

ficient skill to make from plain tubes such forms of glass 
apparatus as are figured|in this work. 

All glass must be carefully annealed after it is made, by 
slow cooling, or it will break in pieces with the least scratch 
or jar. Slow cooling of heated glass for many hours, ox 
even days, is required for heavy articles. Prince Rupert's 
y 00 " drops (fig. 371) are little tears of glass dropped 
yf into water when fused. The outer surface becom- 
il ing solid while the inner parts are still flexible, 

I m there comes to be an enormous strain on the ex* 

^Nr terior, due to the contraction at the centre. If the 

Fig. 371. Y\tt\Q end of this tear is broken, the whole sud- 
denly and with an explosion flies into dust. Unannealed 
glass is to a certain degree under the same conditions of 
unequal tension. Hence the necessity of annealing or slow 
cooling to give time for the* particles to rearrange them- 
selves without strain. Glass is colored red by the oxyds of 
copper and gold, blue by oxyds of cobalt, white by tin, 

How is glass worked in the laboratory ? What is annealing? How is 
this illustrated by Prince Rupert's drops? Explain the illustration. How 
Is glass colored ? 




arsenic and antimony, yellow by uranium, purple and violet 
by manganese, and green by chromium, iron, nickel, &c. 
By the skilful use of these oxyds, with a heavy and highly 
refracting glass, the various gems are very beautifully imi- 
tated. Such imitations are called pastes. 


555. One of the oldest of human inventions is the 
fashioning of vessels of use and ornament out of clay. The 
bricks of Babylon and Nineveh, covered with arrow-head 
inscriptions, are among the most ancient memorials of 

The decomposition of feldspar and other aluminous mine- 
rals and rocks gives origin to the clays which are so import- 
ant in the art of pottery. Decomposed feldspar forms 
porcelain clay, commonly called kaolin. The undecom- 
posed mineral is often ground up to mix with the materials 
for porcelain. The difference between porcelain and earthen- 
ware consists in the partial fusion of the materials of tho 
former by the heat of the furnace, which gives it the semi- 
transparency and great beauty for which it is so highly 
prized. Common earthenware is often glazed with oxyd 
of lead, an unsafe mode for culinary vessels : common salt 
(508) is also used, being raised in vapor by the heat of the 
kiln. The soda unites with silica, while the chlorine escapes 
as chlorid of iron. The glaze in porcelain is formed of a 
more fusible mixture of the same materials, put over the 
articles as a wash, after they have been once through the 
furnace, (in which state they are called biscuit ware;) they 
are then baked again at a' heat which fuses the glaze, but 
which does not soften the body of the ware. All porcelain is 
twice fired and sometimes thrice. If painted, the design is 
laid upon the surface in colors formed from metallic oxyds, 
which develop their appropriate tints only after fusion with 
the ingredients of the glaze. Metallic gold is put on in the 
form of an oxyd, and the steel lustre is produced by metal- 
lic platinum. This beautiful art is carried to a wonderful 

How made refractive ? 555. What is one of the most ancient arts? 
Whence is potter's clay derived ? What is kaolin ? What is the 
difference between porcelain and earthenware ? How is pottery glazed ? 
How porcelain ? How painted ? 




perfection in the royal establishments of France and Prus- 
sia, where the first talent is employed in modelling and paint- 
ing. Any further detail of these interesting branches of 
applied chemistry would be out of place here, and the stu- 
dent is referred to larger works for a fuller description. 

556. There are six other metals belonging to this class, 
which are so rare and comparatively unimportant that we 
pass them with the most cursory enumeration : Glucinum 
is the base of a sesquioxyd G fl O s , (glucina,) which is the 
characteristic earth of the emerald, beryl, and chrysoberyl, 
It is very like alumina, and is named in allusion to the 
sweet taste of its salts. Yttrium is the metal of the earth 
yttria YO, found in the minerals yttrocerite, &c. Zir- 
conium is found as a sesquioxyd of zirconia Zr a 3 in zircon. 
Thoria was found by Berzelius in the rarest of all minerals; 
the thorite, of Sweden. Thorium has the highest specific 
gravity (9) of any earth. Cerium and lantanium are in- 
variably associated, and with them another rare metal, didy- 
mium. The minerals cerite, aUanite, and monazite contain 



Equivalent, 27*6. Symbol, Mn. Density, 8. 

557. Manganese is never found as a metal in nature, but 
may be produced from its black oxyd by a high heat with 
charcoal. Metallic manganese is a gray, brittle metal, not 
magnetic, and resembles some varieties of cast-iron. It dis- 
solves rapidly in sulphuric acid with escape of hydrogen. 

Manganese, in the form of the black oxyd, is an important 
and pretty common metal. Its great use is for producing 
chlorine (282) and in the manufacture of glass, where it 
acts by its oxygen to decolorize the compound. 

558. We enumerate five compounds of manganese, vis. 
protoxyd MnO ; sesquioxyd (or braunite) Mn 9 H ; peroxyd, 
or deutoxyd, (pyrolusite,) MnO fl ; manganic acid MnO t ; 
hypcrmaDganic acid Mn a O r 

656. Enumerate the other earthy metals named in this section. 557. 
What are the equivalent and properties of manganese ? What form of it it 
most common ? For what is it used ? 558. How many and what oxyd! 
if manganese are named? 




The protoxyd is a green-colored powder, formed from 
heating the carbonate of manganese in an atmosphere of 
hydrogen. It is a powerful base, attracts oxygen from the 
air, and is the base of the beautiful rose-colored salts of 

The sesquioxyd or braunite occurs crystallized in octahe- 
drons and forms belonging to the dimetric system. 

The hydrated sesquioxyd Mn a 8 +H0 (manganite) is a 
finely crystallized mineral, in long black prisms, found in 
superb specimens at Ilfeld, in the Hartz. In powder the 
sesquioxyd is brown ; it is decomposed by chlorohydric acid 
with the evolution of chlorine, but sulphuric acid combines 
with it to form a sesquisulphate, which yields a purple 
double salt with sulphate of potash, (manganese alum,) iso- 
morphous with the corresponding salt of alumina. 

559. The peroocyd Mn0 3 is the most common and most 
valuable ore of manganese. From it we* obtain oxygen, and, 
by the decomposition of chlorohydric acid, chlorine. It is 
found abundantly at Bennington, Vermont, and other places 
in this country. When crystallized it is called pyrolusite. 
Beautiful specimens of this mineral have been observed at 
Salisbury and Kent, Connecticut, among the iron ores. 

560. Manganic acid is known only in combination, espe- 
cially as manganate of potash. This is best formed by mix- 
ing equal parts of finely powdered black oxyd of manganese 
and chlorate of potash with rather more than one part of 
hydrate of potash dissolved in a very little water. This 
mixture, when evaporated, is heated to a point short of red- 
ness, and a dark green mass is formed which contains man- 
ganate of potash. In this case the manganese obtains oxygen 
from the chlorate of potash, and the manganic acid thus 
formed combines with potash, giving a salt in green crystals. 
This salt, dissolved in water, gives a brilliant emerald-green 
solution, which almost immediately changes color, being in 
quick succession green, blue, purple, and finally crimson- 
red, and has thence been called chameleon mineral. This 
last color is due to the presence of permanganic acid, which, 
however, cannot be separated from its combinations, but 

Which is the base of the rose-colored salts ? What is the sesquioxyd ? 
Give the formula of the hydrated sesquioxyd? What is said of the sul- 
phate of the sesquioxyd? 559. Which is the most common ore of man- 
ganese ? Where and how is it found ? 560. Describe manganic acid and 
the salt it forms with potash. What is the changeable compound called? 

Digitized by VjOOQ IC 


forms a salt with potash in beautiful purple crystals. The 
compounds of permanganic acid are more stable than the 
manganates. The salts of these acids are respectively iso- 
morphous with sulphates and perchlorates SO, and Cl s O r 

561. The chloruU of manganese MnCl and Mn ? Cl 8 cor- 
respond to the protoxyd and sesquioxyd. The adorid is 
formed abundantly in acting on black oxyd of manganese 
(282) with hydrochloric acid. The mixed solution of chlo- 
rids of iron and manganese is evaporated to dryness, and 
then heated to dull redness. The chlorid of manganese is 
then dissolved out from the dry mass, leaving the insoluble 
protoxyd of iron behind. It has a beautiful pink tint, and 
deposits tabular rose-colored crystals on evaporation. It is 
soluble in alcohol, and fusible by heat. 

562. The salts of manganese are numerous, and in a 
chemical view quite important. Sulphate of manganese 
MnO.SOg-f-THO is a very beautiful rose-colored salt, iso- 
morphous with sulphate of magnesia. It is used to give 
a fine brown dye to cloth, being decomposed by a solution 
of bleaching-powder, which forms the brown peroxyd in the 
fibre of the stuffs. It is also used in medicine. 

Potassa and soda throw down the oxyd of manganese as s 
white powder, which immediately turns brown from the forma- 
tion of a higher oxyd. The carbonates of the alkalies throw 
down carbonate of manganese from their soluble salts. Any 
compound of manganese fused upon a slip of platina with 
carbonate of soda, gives a powerfully characteristic green salt, 
the permanganate of soda. 

Equivalent, 28. Symbol, Fe. Density, 7*8. 

563. Iron is found malleable, and alloyed with nickel, in 
large masses of meteoric origin. One of these, discovered in 
Texas, weighs 1635 pounds, and is now in Yale College 
cabinet. It is not certain that malleable iron of terrestrial 
origin has yet been discovered in nature. Iron is the most 
abundant and most useful metal known to man. Its ores 

What is said of the salts of manganic and permanganic acid? 561. 
Describe the chlorids of manganese ? 562. What is said in general of 
the salts of manganese? What tests are named for manganese and it* 
lalts? 563. What is the equivalent of iron? How is malleable iron 
found? What is said of its abundance and value? 





arc found everywhere, and often in immediate connection 
with the coal and limestone necessary to reduce them to the 
metallic state. There is no soil, and scarcely any mineral, 
which does not contain some proportion of the oxyd of iron. 
We know iron as malleable iron, steel, and cast iron. 

564. To obtain pure iron is not easy, and the best iron of 
commerce is always contaminated with carbon and silicon. 
Small quantities of iron are prepared absolutely pure, in the 
laboratory, by reducing the pure oxyd of iron in a bulb of hard 

Fig. 372. 

glass a b (fig. 372) by a current of dry hydrogen. The bulb 
A is heated by the flame of a spirit-lamp. This apparatus 
serves for numerous reductions of metallic oxyds, as, for 
example, the oxyds of cobalt, nickel, zinc, <fec. The bulbed 
tube a b is drawn down at c (fig. 373) to a narrow neck, 
so that while the tube is yet a 

full of hydrogen it may be seal- 
ed by the blowpipe both at c & &~ 

and b: otherwise the pulverulent Fig- 373. 

metallic iron, from its strong affinity for oxygen, will take 
fire on contact of air, and be carried back again to its original 
condition of oxyd. If this operation is conducted in a por- 
celain tube at a high heat, the iron formed assumes a metallic 
lustre, and does not oxydize ; and if protochlorid of iron is 
used in place of the oxyd, the metal rises in vapor, lining 
the tube with a brilliant crystalline crust. 

665. When quite pure, it is nearly white, quite soft, 'per 
fcctly malleable, and the nltst tenacious of all metals, (471.) 
Its density is 7 8, which may be a little increased by ham- 

564. How is pure iron obtained ? Describe fig. 372. What happens 
if the iron so obtained is exposed to air ? How is it obtained more dense] 
664. What are its properties ? 




mering. It crystallizes in forms of the first class, a» ig 
beautifully shown in the crystalline structure of the meteoric 
iron, and sometimes in the crust produced 
in the reduction of the protochlorid. It 
fuses with extreme difficulty, first becom- 
ing soft or pasty, in which state it is 
welded. When intensely heated in air 
or oxygen gas it combines with oxygen, 
burning with brilliant light and numerous 
scintillations, and is converted into oxyd 
of iron, (fig. 374.) Iron also attracts 
Fig. 374. oxygen from the air at common tempera- 

tures, forming rust. This does not happen in dry air, but 
the presence of moisture, and particularly of a little acid 
vapor, very much promotes its formation. Iron decomposes 
water very rapidly at a red-heat, hydrogen being evolved. 
Its magnetic relations have already been fully explained. 
Cobalt and nickel are the ouly other magnetic metals. 

566. The oxyds of iron aro three, viz : 1. Protoxyd, 
FeO; 2. Sesquioxyd, commonly called peroxyd, Fe 8 8 ; 
3. Ferric acid, Fe0 8 . The magnetic oxyd Fe 3 4 is regarded 
as a compound of protoxyd and sesquioxyd FeO.Fe^Oj, in 
which the sesquioxyd plays the part of a base, (475.) 

1. The protoxyd of iron FeO is a powerful base which 
is unknown in nature except in combination. It saturates 
acids completely and is isomorphous with a large class of 
bodies, of which zinc and magnesia are examples, (263.) 
This oxyd is thrown down from its solutions by potash, as 
a whitish bulky hydrate, that soon gains another portion 
of oxygen from the air, becoming brown, and finally red. 
Its salts, when soluble, have a styptic taste like ink, and a 
greenish color, of which the most familiar example is green 
vitriol y or sulphate of protoxyd of iron. 

2. The peroxyd of iron Fe a 8 is found native in the 
beautiful specular iron of Elba, and also in the red and 
brown hematites. Limonile 2(Fe a 8 )+3HO is a hydrous 
sesquioxyd. It is slightly acted on by the magnet, and 
after ignition is almost insolublefin strong acids. It is iso- 
morphous with alumina, and is generally associated with it 
in soils and many minerals. It is often of a brilliant red, 

What is welding ? 566. What oxyds are named ? Give their formulas. 
Describe the protoxyd and its salts. How is the peroxyd known ? 



ikon. 833 

and, as ochre of various tints, is much used as a pigment 
Ammonia, potassa, or soda precipitates it from its solutions 
as a bulky red hydrate, which, in its moist condition, is 
esteemed an antidote to poisoning by arsenic. Colcothar, 
or rouge, is this oxyd prepared by calcining the sulphate : it 
is much used in polishing metals. 

Magnetic oxyd of iron Fe 8 4 is familiarly known in the 
common magnetic iron ore and native lode-stone. It crys- 
tallizes in octahedrons. It forms no salts, and, as has al- 
ready been remarked, is regarded as a salt of FeO+Fe a O t . 
The finery cinders or scales thrown off under the smith's 
hammer are this oxyd. 

3. Ferric Acid, Fe0 8 . — This compound, discovered by M. 
Fremy, corresponds to manganic acid. Ferrate of potash is 
formed when one part of peroxyd of iron and four parts of 
nitre are heated to full redness in a covered crucible for an 
hour. The ferrate of potash is dissolved out of the porous 
mass by ice-cold water. The solution has a deep amethyst- 
ine color, and is easily decomposed by heat. A soluble 
salt of baryta precipitates ferric acid as a beautiful red fer- 
rate of baryta, which is permanent. 

567. The chlorids of iron FeCl and Fe a Cl 8 correspond to 
the protoxyd and sesquioxyd of the same base. The per- 
chlorid is often used in medicine, and may be formed by 
saturating hydrochloric acid with freshly prepared peroxyd 
of iron. The protiodid of iron is also a valuable medicine. 

The sulphurets of iron are found in nature, and are known 
under the mineralogical names of pyrites and marcasite 
FeS s , and magnetic pyrites Fe.S s . The protosulphuret FeS 
is easily formed artificially, t>y fusing sulphur with iron 
filings: they ignite with a vivid combustion, and proto- 
sulphuret of iron is formed, which is much used in pre- 
paring sulphuretted hydrogen. Yellow iron pyrites and 
white iron pyrites (marcasite) are dimorphous forms of the 
bisulphuret FeS a : the first is one of the most common of 
crystallized minerals. 

568: Of the salts of iron, green vitriol, or copperas, a pro- 

What is colcothar ? Giro the formula of the black oxyd. How is it found 
in nature ? What is ferric acid ? 567. What chlorids of iron are named t 
What oxyds do they correspond to ? What are the sulphurets of iron ? 
For what is the protosulphuret used ? What is the name of the ordinary 
•ulphuret? What two forms of it are found in nature? 




tosulphate FeO.S0 8 +7HO, is the most important. It i* 
made in immense quantities, as at Stafford, Vt , from the 
fermentation of iron pyrites, which furnishes both the acid 
and the base. This salt crystallizes beautifully, and is 
much used as the basis of all black dyes and of ink, and in 
the manufacture of prussian blue. Persulphate of iron is a 
sulphate of the peroxyd Fe a O,+3SO,. Carbonate of iron 
occurs in nature as spathic iron ore, which is isomorphous 
with carbonate of lime. A variety of steel is made directly 
from this ore without cementation, (570.) It is formed 
artificially by precipitating a solution of protosulphate by 
an alkaline carbonate. It is used in medicine. 

Water containing carbonic acid dissolves protozyd of iron 
and acquires the well-known flavor of chalybeate waters : 
exposure to air permits the escape of the carbonic acid, 
when the iron falls as red peroxyd. 

Phosphate of iron FeO.P0 5 +8HO is formed as a green- 
ish-white gelatinous precipitate when solution of tribasio 
phosphate of soda is added to solution of protosulphate of 
iron. It is an article of the materia medica. Yivianite 
is a mineral having the same formula, found both massive 
and crystallized, of a beautiful indigo-blue color. 

The cyanogen compounds of iron will be described in the 
organic chemistry. 

The presence of a salt of iron is easily detected by the 
fine blue ('prussian blue) formed on adding prussiate of 
potash to the solution : an infusion of galls gives a black 
color (ink) to solutions of iron salts. 

569. The chief ores of iron are, 1. The specular iron or 
peroxyd, including red and brown hematite; 2. Limonite, or 
hydrous peroxyd, from which the best iron is made — (bog 
iron also comes under this head ;) 3. Clay iron-stone, which 
is an impure carbonate of iron, or carbonate of iron with 
carbonate of lime and magnesia — this is the nodular ore and 
band ore of the coal formations ; 4. Black or magnetic oxyd 
of iron, which is the ore of the iron mountains of Missouri 
and of Sweden. 

The reduction of the ores of iron to the metallic state it 
asually performed in large furnaces called high or blast fur- 

568. Which of the salts of iron is of great importance ? How and 
where is it made in this country ? What is the carbonate and for what 
used ? What of the phosphate ? What tests are named for iron ? 569. What 
ores of iron are onumerated ? How is the reduction of iron effected ? 





naces. These are built of stone, 
in a conical form, 30 to 50 feet 
high, and lined internally with 
the most refractory fire-bricks. 
The furnace is divided into the 
throat, the fire-room b, the 
boshes e, (that portion sloping 
inward,) the crucible t y and 
the hearth A. The blast of 
air — supplied from very large 
blowing cylinders — is intro- 
duced by two or three tuyere^ 
pipes a a, near the bottom. In 
the most improved furnaces, the 
air-blast is heated by causing a^_ 
it to pass through a series of j , 
pipes in the upper portion of the Jil 
furnace, so as to have a temper- Fig. 375. 

ature of 500° or more when it enters the furnace. When 
the furnace is brought into action, it is first heated with 
.coal only, for about 24 hours, to raise it to the proper tem- 
perature ; and then is charged alternately with proper pro- 
portions of coal, roasted ore, and lime for flux, until it is 
quite full. When once brought into action, the blast is 
kept up for months or even years, until the furnace requires 
repairing. The ore is reduced on the boshes, and in the 
upper part of the crucible, where the oxyd of carbon is found 
almost pure in presence of an excess of white-hot carbon and 
ore previously dried and in part reduced in the higher parts 
of the furnace. The melted metal collects on the hearth, 
where it rests, covered by the molten flux, which is a glass, 
formed by the fusion of the lime used, with the earthy parts 
of the ore. From time to time, the iron is drawn off by an 
opening level with the hearth, previously stopped with clay, 
and run into rude open moulds in sand. This is cast iron, 
and is of various qualities, according to the various charac- 
ter of the ore and the working of the furnace. If malle- 
able bar iron is wanted, the cast iron is again melted, in 
what is called the puddling furnace, where it is stirred 

Describe the high furnace. What is the hot blast? What is the ope- 
ration of the furnace ? What is cast iron ? How is malleable iron mads 
from cast iron ? 




about by an iron rod, in contact with oxyd of iron, and a 
current of heated carbonic oxyd from burning wood or coal. 
It gradually becomes stiff and pasty from the burning out 
of the carbon, and from some molecular change not well 
understood. This pasty condition increases until the iron 
is finally raised in a rude ball and placed under the blows 
of a huge tilt-hammer, when the scoria is pressed out and 
the particles made to cohere. It grows tenacious by a repe- 
tition of this process, being cut up and piled or faggoted and 
reheated several times, until it is finally rolled in the roll- 
ing-mill into tough and fibrous metal. 

570. Steel is formed from refined iron by heating it for 
days in succession in contact with charcoal in close vessels, 
(called cementation.) It gains from ono to two per cent 
of carbon, becomes fusible, and can be tempered according 
to the use for which it is designed. 

The Catalan forge is a furnace formed like a smith's forge 
on a large scale, and in which the circumstances of the high 
and puddling furnace are combined, so that malleable iron 
is produced from the ore — the cast iron being brought to 
the ductile state in the same fire where it is reduced from 
the ore — charcoal is the fuel of the Catalan forge. The 
best iron is always produced when charcoal is the fuel, being 
free from sulphur and phosphorus, the two worst enemiei 
of good iron. 

Equivalent, 26*4. Symbol, Cr. Density, 6. 

571. Chromium in combination with iron is rather an 
abundant substance, particularly in this country, being found 
as chromic iron at Barehills, near Baltimore ; Lancaster Co., 
Pa., and in several other places. The beautiful red chro- 
mate of lead is also a natural product in Siberia. The 
metal, from its great affinity for oxygen, is very difficult to 
procure. It is a hard, almost infusible substance, resem- 
bling cast iron, nearly insoluble in acids, and does not 
decompose water. It may be oxydized by fusion with nitre, 
but does not change in the air. 

570. What is steel? What is the Catalan forge? What fuel makes 
the best iron? 571. What are the symbol and properties of chromium? 
How distributed in nature ? 




" 572. The oxyds of chromium are exactly the same as 
those of manganese. Chromium bears the strongest analogy 
in its chemical character to manganese and iron. The pa- 
rallelism of constitution in the oxyds of these three metals 
is shown in the following tabular arrangement : — 

Protoxyd. Sesquioxyd. Black oxyd. Peroxyd. , * ■■■■^ 

Manganese forms.. MnO ... Mn»0, ... Mn,0« ... MnO a MnO, Mn«0« 

Iron forms. FeO ... Fe,0, ... Fe,0 4 ... FeO, 

Chromium forms...CrO ... Cr,0, ... Cr,0« ... CrO» CrO, Cr»O f 

The protoxyd of chromium is a strong base, acting in 
combination like the protoxyd of iron, with which it is iso- 

573. Sesquioxyd of chromium Cr a 3 may be obtained 
in little rhombohedral crystals by passing the vapor of chlo- 
rochromic acid through a heated tube, 2CrO a Cl = Cr a O s -f- 
2C1-J-0. The crystals are deposited on the walls of tho 
tube in a brilliant deep-green crust. They are as hard as 
ruby. Their density is 5*21. 

The hydrated sesquioxyd of chromium Cr a 3 +HO is 
easily prepared by treating a boiling and rather dilute solu- 
tion of bichromate of potash with an excess of chlorohydric 
acid, and then wi£h successive portions of alcohol or sugar 
until it assumes a fine emerald tint. Ammonia throws down 
a bulky, pale-green precipitate, soluble in acids and shrink- 
ing very much in drying — this is the hydrate. On ignition 
it undergoes vivid incandescence and becomes deep green. 
The sesquioxyd of chromium is a feeble base like those of 
iron and alumina, and may replace them in combination, as 
in the formation of chrome alum with sulphate of potash. 
Sesquioxyd of chromium forms an alum also with the sul- 
phates of soda and ammonia. All the salts of this oxyd 
are either emerald green or bluish purple. It imparts a 
rich tint of greeu to glass and porcelain, and is the cause 
of the color of the emerald. Chrome iron is composed of 
this oxyd and protoxyd of iron FeO.Cr a O a , isomorphous with 
magnetic iron FeO.Fe fl 3 , and with spinel MgO.Al a 8 . The 
chrome iron of Pennsylvania contains a little nickel. 

574. Chromic acid Cr0 8 is readily formed by treating 

572. What strong analogies has it ? Give the parallel oxyds of Mn, Fe, 
and Cr. 573. How is sesquioxyd of Cr obtained ? How is its hydrate ? 
What are its properties ? What salts does it form ? What is chrome iron ? 
574. How is chromic acid formed ? 




a cold and concentrated solution of bichromate of potash 
with one and a half parts of sulphuric acid. The mixture, 
when cold, deposits brilliant ruby-red prisms of chromic 
acid. The sulphate of potash in solution above, may be 
turned off, and the chromic acid dried on a porous brick, 
being carefully covered with a glass to prevent access of 
organic matters, which at once decompose it. If a little of 
this acid be thrown into alcohol or ether, the violence of the 
action is such as to set fire to the mixture. Chromic acid 
forms numerous salts, which are highly colored. 

The protochlorid of chromium CrCl is obtained as a 
white and very soluble substance by the action of dry hy- 
drogen gas on the sesquichlorid. The tesquichloritl Cr a Cl 9 
is prepared by passing chlorine gas over an ignited mixture 
of the sesquioxyd and charcoal. It forms a crystalline 
sublimate of a peach-blossom color, which is insoluble in 
water. The sesquioxyd dissolves in chlorohydric acid, 
but the hydrated chlorid thus obtained is decomposed by 

Ghlorochromic acid Cr0 3 Cl is a deep-red volatile liquid, 
much resembling bromine in its appearance. It is formed 
when 10 parts of common salt and 17 of bichromate of 
potash are intimately mixed, and heated in a retort with 
30 parts of concentrated sulphuric acid. The chlorochromic 
acid distils over, filling the receiver with a superb ruby-red 
vapor. Its density is 1*71, and it boils at 248°. Water 
decomposes it, forming chromic and hydrochloric acids. It 
may be preserved in tubes hermetically sealed. 

675. The chromate and the bichromate of potash arc both 
familiar compounds of chromic acid. The first, K0.Cr0 3 , i& 
formed on a very large scale, by decomposing the native 
chromic iron with nitrate of potash, by aid of heat, Chro- 
mate of potash is dissolved out from the ignited mas a, and 
crystallizes in anhydrous yellow crystals. It ia is amorphous 
with sulphate of potash, dissolves in two parts of cold water, 
and is the source of all the preparations of chromium. 

Bichromate of potash K0.2Cr0 8 is formed by adding 
sulphuric acid to a solution of the yellow ehr ornate, when 
half the potash is removed, and the bichromate crystallises 

Give its properties. Describe the chlorids of chromium. Describe chlo* 
rochromic acid. 575. How is chromate of potash formed ? How is bi- 
chromate of potash formed ? 



NICKEL. 339 

by slow evaporation in brilliant red* crystals of a rhombic 
form, which are soluble in ten parts of cold water. 

576. ChromateofLead— Chrome YeUow— (PbO.Cr0 8 )is 
*he well-known pigment prepared by precipitating the nitrate 
or acetate of lead by a solution of chromate or bichromate 
of potash. Chrome Green is the oxyd of chrome, prepared 
in a particular way. 


Equivalent, 29*6. Symbol, Ni. 

577. Nickel is rather a rare metal. It is prepared from 
the speiss or crude nickel of commerce. It is white and 
malleable, having a density of 8 to 8*8, and fuses above 
3000°. Reduced from its oxyd by hydrogen (fig. 373) at a 
low temperature, it takes fire in the air. The compact metal 
is not easily oxydized. It is the only metal beside iron and 
cobalt which is magnetic. This property it loses when heated 
to 700°. Meteoric iron almost invariably contains nickel, 
Sometimes as much as 10 per cent. Its chief ores are cop- 
jper-nickel and speiss-cobalt. 

Arseniuret of nickel and cobalt is found at Chatham, 
Conn., and oxyd of cobalt and manganese in Mine-la-Motte, 
Mo. The emerald nic7cel y a beautiful green hydrous car- 
bonate described by the author, is found in Lancaster Co., 
Pa. Its formula is 3(NiO)C0 2 +6HO. 

578. There are two oxyds of nickel. The protoxyd NiO 
is prepared by precipitating a solution of nickel by caustic 
potash : this is soluble in ammonia. It gives a grass-green 
hydrated oxyd, which, by heat, loses its water and becomes 
gray. The oxyd of nickel is isomorphous with magnesia, 
and has been obtained crystallized in regular octahedrons. 
The salts of this oxyd have a fine green color, which they 
impart to their solutions. 

The peroxyd of nickel NiO a is a dull black powder, of 
no particular interest. 

579. The sulphate of nickel NiO.S0 3 +7HO is a finely 
crystallized salt, occurring in green prisms, which lose their 

576. What is chrome yellow? What chrome green? 577. In what 
state does nickel occur in nature ? Describe its properties. What of its 
magnetic property ? 578. What are oxyds ? In what form does the prot- 
oxyd crystallize ? 579. Describe the sulphate and oxalate of nickel. 




water of crystallization by heat. It forms beautiful, well 
crystallized double salts, with the sulphates of potash and 
ammonia. Oxalic acid precipitates an insoluble oxalate of 
nickel from the solution of the sulphate, and the metallic 
nickel is easily obtained from the oxalate by heat. 

Nickel is chiefly employed in making German silver, a 
white malleable alloy, composed of copper 100, zinc 60, and 
nickel 40 parts. 


Equivalent, 29-5. Symbol, Co. 

580. Cobalt is a metal almost always associated with 
nickel, and closely resembling it in many of its reactions. 
When pure it is a brittle, reddish-white metal, with a density 
of 8*53, and melts only at very high temperatures. It is 
nearly as magnetic as iron. It dissolves with difficulty in 
strong sulphuric acid, and is not oxydized in air. It form* 
two oxyds every way analogous to those of nickel. Its prot- 
oxyd is a grayish-pink powder, very soluble in chlorohydric 
acid. It forms pink salts. This oxyd occurs native. 

The chlorid of cobalt CoCl is formed by dissolving the 
oxyd in hydrochloric acid. The solution is pink, and when 
very dilute may be used as a blue sympathetic ink, which 
may be made green by mixing a little chlorid of nickel. 
Writing made with this on paper is colorless when cold, but 
becomes of a fine blue or green when gently warmed, and 
loses its color again on cooling. 

The salts of cobalt and nickel are isomorphous with those 
of magnesia. They are not thrown down by sulphuretted 
hydrogen, but give blue or green precipitates with potash, 
soda, and their carbonates. The same precipitates with 
ammonia are soluble in excess of that reagent. Oxyd of 
cobalt imparts a splendid blue to glass, and the pulverized 
glass of this color is called smalt and powder blue. Zaffre 
is an impure oxyd of cobalt, used to give the blue color to 
common earthenware. 

What is the composition of German silver ? 580. What are the charac- 
ters of cobalt? What interesting experiment is mentioned with the 
chlorid ? With what oxyd are the oxyd of cobalt and its salts isomor- 
phous ? What use is made of the oxyd of cobalt ? 






Equivalent, 32-.5. Symbol, Zn. Density, 6-86 to 7*20. 

581. Zinc is an important and rather common metal. It 
is not fonnd native, but a peculiar red oxyd of zinc abounds 
at Sterling, New Jersey, and calamine or carbonate of zino 
is found abundantly in many places. The ores of zinc are 
reduced by heat and charcoal, in large crucibles closed at 
top, but haying a clay tube a b 
descending from near the top, as in 
fig. 376, through the crucible and its 
support B, to a vessel of water C. 
The cover is luted on and the heat 
raised. The metal, being volatile, 
rises in vapor, which descending 
through the tube, is condensed in 
the water below. This is called 
distillation per descensum. 

582. Zinc is a bluish-white metal, 
easily oxydized in the air, and crys- 
tallizes in broad foliated laminae, 
well seen in the fracture of an ingot g * 376# 

of the commercial metal. It is called spelter in the arts, 
and is largely used to alloy copper in forming brass, to form 
sheet zinc, and also for the protection of iron in what is called 
galvanized iron. Zinc is not a malleable metal at ordinary 
temperatures, but at a temperature of between 250° and 300° 
it becomes quite malleable, and is then rolled into sheet 
zinc. At about 390° it is again quite brittle, and may be 
granulated by blows of the hammer : at 773° it melts, and 
if air has access to it, it takes fire, and burns rapidly with a 
brilliant whitish-green flame, giving off flakes of white oxyd 
of zinc, anciently called lana philosophica and pompholix. 
It is completely volatile at a red heat. We constantly em- 
ploy zinc in the laboratory to procure hydrogen, and granu- 
late it by turning it slowly into cold water from some height. 
It dissolves in solutions of soda and of potassa, with evolu- 
tion of hydrogen and formation of zincate of the alkali 

583. The oxyd of zinc ZnO is formed when zinc burns 

5S1. Hew is sine reduced from ite ores? How distilled? 582. Whai 
arc it* properties ? At what temperature is it malleable ? 




in air. Only one oxyd is known. It is, when pure, a white 
powder, yellowish while hot. It contains zinc 80*26, oxygen 
19*74. It is insoluble in water, but forms a hydrate with it. 
The anhydrous oxyd mingled with drying- oils forms a valu- 
able paint, now coming into use in place of white-lead. It 
has the advantage of not changing by sulphuretted hydro- 
gen and of not being deleterious to the health of the work- 
men. It is now largely manufactured from the red zinc of 
New Jersey, and from the franklinite of the same region, 
which contains a large quantity of zinc. 

Calamine is a native carbonate of zinc ZnO.CO fl , and 
is its most valuable ore. Electric calamine is a silicate 
8(ZnO)SiO s +l}HO. 

Chlorid of zinc ZnCl is a valuable escarotic, and has 
been much used in dilute solution to preserve anatomical 
subjects for dissection. 

Sulphuret of zinc, Blende, ZnS, is one of the most common of 
the ores of zinc. It occurs in beautiful brilliant crystals, modi- 
fications of the first system, called by the miners black-jack. 

Sulphate of Zinc, or White Vitriol, ZnO.S0 8 +7HO.-— 
This salt has the same form as the sulphate of magnesia, and 
looks extremely like it. It dissolves in 2} parts of cold 
water, at 60°, but at 212° is indefinitely soluble, as it then 
fuses in its own crystallization water. It forms double 
salts with the sulphates of ammonia and potash. It is a 
powerful and very rapid emetic. 

Sulphuret of ammonia throws down a characteristic white 
precipitate of sulphuretted zinc from its neutral solutions 

Equivalent, 56. Symbol, Cd. Density, 8*7. 
584. Cadmium is generally found associated with zinc. 
It is quite malleable, white, and harder than tin. It fuses 
at 442°, and volatilizes completely at a temperature a little 
above this. It is not easily oxydized, and is but slightly 
soluble in chlorohydric or sulphuric acid*. Nitric acid dis- 
solves it with ease, forming a salt from which sulphuretted 
hydrogen throws down a very characteristic orange-yellow 
sulphuret. This compound is also found native and crys- 
tallized, (greenockite.*) 

583. Describe the oxyd ZnO. What large use is being made of it? 
What is calamine ? Blende ? Sulphate of zinc ? What of its solubility ? 
584. What are the properties of cadmium ? 



LEAD. 843 

Its oxyd CdO is a bronze powder, formed by igniting tho 
nitrate or carbonate, and rises in a brown vapor when cad- 
mium is placed in the focus of the oxyhydrogen blowpipe. 


Equivalent, 103*5. Symbol, Pb. Density, 11-45. 

585. This useful and familiar metal occurs in boundless 
profusion in this country. Its chief ore is galena, or sul- 
phuret of lead, from which the metal is easily obtained by 
smelting with a limited amount of fuel at a low heat. The 
carbonate, phosphate, chromate, and arseniate are also na- 
tural salts of lead, much prized by the mineralogist. 

Lead is a bluish-gray metal, very soft and ductile, but not 
very tenacious, (471 ;) it oxydizes in the air quite rapidly, 
forming a coat of oxyd, or carbonate, which usually protects 
it from further corrosion. Its destiny is 11-45, and it fuses 
at about 630°; when melted it combines rapidly with oxygen 
from the air, forming either protoxyd, or red oxyd, accord- 
ing to the degree of heat employed. It is somewhat volatile 
above a red heat. 

Lead is acted upon by distilled water and by rain water. 
Water, by reason of its affinity for the oxyd of lead, acts 
like an acid upon metallic lead. A bright slip of pure lead 
is tarnished almost immediately in pure water, and after a 
short time becomes covered with a pellicle of carbonate of 
lead ; while the water yields a dark cloud to sulphuretted 
hydrogen, showing the presence of oxyd of lead dissolved in 
it. It is, therefore, unsafe to use water-pipes of lead, unless 
it has been proved by experiment that the particular water 
in question does not act on this metal. The carbonate, which 
is the salt generally produced under these circumstances, is 
an energetic poison. The presence of a very small quantity 
of foreign matter in water, and especially of the sulphate of 
lime, usually arrests this action, and renders the use of lead- 
pipes in a majority of cases not hazardous. 

Lead does not easily dissolve in strong acids, except in 
nitric, with which it forms a soluble salt : strong sulphuric 
acid dissolves it only when heated, forming nearly insoluble 
sulphate of lead. 

685. What is the chief ore of lead ? What are the properties of lead? 
Its density and fusion point? Is it volatile ? What acts on lead ? What 
salt of lead is most poisonous ? What arrests the action of water on V«* • 





Th ire are three oxyds of lead, viz. suboxyd Pb a O, prok 
oxyd PbO, and peroxyd, or plumbic oxyd PbO a . 

586. Protoxyd of Lead, Litharge, Massicot, PbO. — This 
oxyd is a yellow powder, formed by slowly oxydizing lead 
with heat. It is slightly soluble in water, and the solution 
is alkaline : in solution of sugar it is largely soluble. It 
fuses easily, and dissolves silica with great rapidity; hence its 
use in glazing pottery (555) and in the manufacture of glass, 
(553.) It forms a large class of definite salts, which have 
often a sweet tafcte, as is seen in the acetate, or sugar of lead. 
The peroxyd Pb0 9 is prepared by acting on the red-lead 
. with dilute cold nitric acid : it is a puce-colored body, which 
plays the part of an acid, forming salts with bases. The 
oxyd of lead forms insoluble salts with the fatty acids, of 
which the well-known diachylon plaster is an example. 
There are several intermediate oxyds of lead, called miniums 
which are of variable composition, according to the tempera- 
ture at which they are prepared. Red-lead is a familiar ex- 
ample of these. Its formula is Pb 3 4 or 2PbO.Pb0 9 . It 
has a fine orange-red color when well prepared, and is some- 
times found crystallized in the fissures of the furnaces. It 
is prepared by exposing lead to a constant temperature of 
about 700°. Acted on by hydrochloric acid, it evolves 
chlorine, and, with sulphuric acid, oxygen is given off. It 
is preferred to litharge for glass-making. 

The chlorid and iodid of lead possess no particular inte- 
rest ) the latter crystallizes in beautiful yellow scales from 
its solution in hot water. The chlorid, iodid, 
and sulphate are all very insoluble compounds. 
Sulphuretted hydrogen throws down a black 
sulphuret from all soluble salts of lead, being 
the best test of its presence. 

587. Zinc precipitates it from its solutions by 
voltaic action, in beautiful crystalline plates of 
metallic lead, which assume a branching form, 
often an inch or two in length, and hence called 
the lead-tree, or arbor satumi, from the alche- 
Fig. 377. m i s tic name of this metal. The acetate is usually 
employed : an ounce of the salt is dissolved in two quarts of 

What oxyds of lead are there ? 586. What names has PbO ? Give 
its properties. What is PbO a ? What is diachylon plaster? What are 
the miniums ? What use is made of minium ? What test lb named for 
lead salts ? 587. How is metallic lead precipitated from its solution ? 



copper. 345 

distilled water, and a piece of clean zinc suspended in it by 
a thread : the precipitation is gradual, and occupies one or 
two days. . The arrangement is seen in the fig. 377. 

588. Carbonate of Lead, White-lead) Ceruse, PbO.C0 3 . 
— This salt is found beautifully crystallized in nature, but 
is prepared artificially in very large quantities, for the pur- 
poses of a paint. This pigment is obtained by casting lead 
in very thin sheets, which are then rolled up into a loose 
scroll Z (fig. 378) and placed in a pot over a small quantity 
of vinegar u, supported on the ledge b b, so 
as not to project above the pot, nor touch the ~ 
vinegar. The vinegar is obtained from the 
fermentation of potatos. Many thousands of 
these pots are arranged in successive layers 
over each other, with covers n! m between, and 
the interstices filled with spent tan, or ferment- 
ing stable-dung, which gives a gentle heat to 
the acid. After a time the lead is completely g * ' 
converted into an opake white crust of carbonate. The theory 
of this process will be explained when we describe the ace- 
tates of lead, (Organic Chemistry.) White-lead is now largely 
adulterated by sulphate of baryta, but the fraud may be 
easily detected by dissolving the carbonate in an acid, when 
the sulphate of baryta will be left behind. Carbonate of 
lead is highly poisonous. 

589. Uranium, (equivalent 60.) — This rare metal is found 
only in a few very rare minerals, of which the best known are 
pitch blende, an impure oxyd of uranium, and uranite, one 
of the most beautiful of mineral species, which is a phos- 
phate of uranium. The metal is of a silver color, a little 
malleable, and has so great an affinity for oxygen as to burn 
in the air. It forms two oxyds, UO and U 9 r The salta 
of uranium possess considerable chemical interest. 


Equivalent, 31*7. Symbol, Cu. Density, 8-87. 

590. Capper has been in familiar use since the times of 
Tubal Cain, and is one of the most important metals to the 

588. How ia the carbonate prepared, and for what is it used ? 589. In 
what minerals is uranium found ? What oxyd does it form ? 590. Whai 
it the history of copper ? 




wants of society. It is often found in the metallic slate* 
The metallic copper of Lake Superior is found in irregular 
veins, filling fissures, from which it is cut by chisels, and by 
drills in huge blocks of great purity. Small masses of 
silver are also often found adherent to the copper. One 
mass from this region, now at Washington, weighs over 3000 
pounds, and such masses are frequent. The most usual 
ores of copper are the red oxyd of copper, copper pyrites, 
and copper glance, a pure sulphuret, or sulphuret of copper 
and iron. 

The blue and green malachites, or carbonates of copper, 
phosphate and arseniate of copper, and many other salts of 
this metal, are also found in the mineral kingdom. Copper 
is very malleable, and is the only red metal except titanium. 
It fuses at 1996°, and has a density of 8*78, which may 
be increased to 8 -96 by hammering. It does not change in 
dry air, but in moist air becomes covered with a green coat 
of carbonate, known as verdigris, (corruption of the French 
vert de gris.) It is stiffened by hammering or rolling, and 
softened again by heating and quenching in water. It may 
be drawn into very fine wire of good tenacity, which is an 
excellent conductor of heat and electricity, and is much 
used in electro-magnetism and for the telegraphic conductors. 

Nitric acid is the proper solvent of copper, sulphuric and 
hydrochloric acids scarcely acting upon it. 

591. There are four oxyds of copper, suboxyd Cu s O, 
protoxyd CuO, binoxyd CuO^, and an acid oxyd whose 
composition is unknown. * 

The protoxyd, or black oxyd of copper, CuO, is the 
base of all the blue and green salts of copper. It is 
formed by decomposing the nitrate with heat. It is black 
and very dense, quite soluble in acids, and forms many 
important salts which are isomorphous with those of mag- 
nesia. It yields all its oxygen to organic matters at a red 
heat, and for this purpose is much used in their analysis. 

The suboxyd, or red oxyd of copper, Cu a O, is found 
native in beautiful octahedral crystals, and is also formed 
when copper is oxydized by heat. This oxyd communicates 

How found at Lake Superior? What copper ores are named? Give 
its equivalent and characters. What is the solvent of copper? 591. 
What oxyds of copper are known ? What relative to the black oxyd 
of copper ? Describe the suboxyd. 





to glass a magnificent ruby-red color. The chlorids and 
iodids of copper are of no great importance. 

592. Sulphate of copper, blue vitriol, CuO.S0 8 +5HO, 
is an important salt, crystallizing in large, beautiful blue 
rhombs, which are soluble in four parts of cold and two 
parts of hot water. It loses its water by a gentle heat and 
falls to a white powder. It is much used in dyeing and for 
exciting galvanic batteries. With ammonia it forms a dark- 
blue crystallizable compound. 

593. Nitrate of copper CuO.N0 5 +3HO is formed by 
dissolving copper in nitric acid to saturation, and is a deep- 
blue, crystallizable, deliquescent salt, very corrosive, and 
easily decomposed : a paper moistened with a strong solu- 
tion of this salt cannot be rapidly dried without taking fire, 
from the decomposition of nitric acid. The residues of 
operations for obtaining deutoxyd of nitrogen (341) afford 
an abundant supply of this salt in the laboratory. 

Ammonia detects the smallest traces of this metal in 
solution, by the deep violet-blue of the ammoniacal salt of 
copper which is formed. Iron precipitates it from its acid 
solution as a brilliant red coating. Copper is a metal most 
readily obtained in a metallic form from its solutions by 
voltaic decomposition. The sulphate is usually employed for 
this purpose in the electro- 
type, the arrangement be 
ing made like fig. 379, the 
operation of which has 
been already explained in 
section 234. The alloys 
of copper are much prized 
for their various useful 
applications in the arts. 
Brass is zinc &, copper i . 
Dutch metal, of which thin 
leaves are made, contains 
10 to 14 of zinc. 

Fig. 379. 

592. Describe the sulphate of copper. 593. What is the nitrate ? How 
does it affect organic matter ? How is copper detected? Why is cop- 
per used in electrotyping ? What of its alloys ? 





594. The five first metals in this class are so rare that 
we may pass them with a very brief mention. They are 
vanadium, tungsten, columbium, titanium, and 

Vanadium appears to be closely allied to chromium. 
The vanadic acid V0 8 fornjs salts with lead and copper, 
found native as vanadinite, and volborthite CuO. V0 8 . 

Tungsten, so named from its great weight, (12*11,) exists 
as tung3tic acid W0 8 in wolfram and schedetine CaO.W0 8 
or tungstate of lime. . Native tungstic acid has been observed 
in Monroe, Conn. : it is a yellow powder, soluble in ammo- 
nia, but insoluble in acids. 

Columbium, or tantalum, is the metal of a mineral called 
columbite, (in allusion to its American origin, by Hatohett, 
its discoverer,) or tantalite, a salt of iron in which this metal 
is the acid. It forms two oxyds, TaO fl and Ta0 8 , both acids. 
It is with the columbite of Haddam that the, two new 
metals, pdopium and niobium, are found, as described by 

Titanium is a copper-red metal, crystallizing in cubes. 
It forms with oxygen titanic acid TiO fl , a substance found 
pure in three distinct minerals, viz. rutile, anatase, and 
Brookite, an interesting case of trimorphism. This acid is 
soluble in strong chlorohydric acid, but precipitates, on di- 
lution and boiling, a white, insoluble powder, much resem- 
bling silica. It is used to give a yellowish tint to porcelain 
in preparing artificial teeth. 

Molybdenum is a white, slightly malleable, infusible metal, 
density 8*6. The sulphuret is a common mineral distributed 
in primitive rocks: it resembles graphite. It forms with 
oxygen oxyd of molybdenum MoO, binoxyd MoO fl , and mo- 
lybdic acid MoO s , which is its most important compound* 
Molybdic acid forms soluble salts with the alkalies, of which 
the molybdate of ammonia is the most valuable, being the 

594. What is vanadium ? What is tungsten ? In what minerals found ? 
What is columbium ? In what mineral found ? What new metals hare 
been found with it? What is titanium? What is titanic acid? What 
natural forms has it ? How is molybdenum found in nature ? What im- 
portant salt does it form ? 



tin. 349 

most delicate test known for phosphoric acid. Molybdate of 
Jead is a beautiful native salt of this acid. Heat converts 
the sulphuret into the impure acid, and it is also oxydized 
directly by monohydrated nitric acid. 

tix. f 

Equivalent, 59. Symbol, Sn, (Stnanum.) Density, 7*29. • 

595. Tin is one of those metals which have been known 
from the most remote antiquity. The mines of Cornwall 
have been worked for the oxyd of tin since the times of the 
Phoenicians and Greeks. It has been found in this country 
only at Jackson, N. H., in small quantities. Tin is a white 
metal with a brilliant lustre, not easily tarnished, and resist- 
ing the action of acids to a remarkable degree. It is soft, 
very ductile, laminable, malleable, but of feeble tenacity. 
Tin foil is made of one-thousandth of an inch in thickness, 
or even much thinner. A bar of tin when bent gives a pe- 
culiar crackling sound, familiarly called the cry of tin, due 
to the disturbance of its crystalline structure. It is one 
of the best conductors of heat and electricity. 

596. Tin has a density of 7*29, and fuses at 442°. Its 
alloys are very valuable ; gun-metal (copper 90, tin 10) is 
one of the strongest alloys known, of a reddish-yellow ; bell- 
metal (copper 78, tin 22) is a very sonorous and brittle 
alloy, of a pale yellow ; and speculum-metal (copper 70 to 
75, and tin 25 to 30) is a hard, brilliant, almost white, and ex- 
cessively brittle alloy. Pewter is a mixture of tin and anti- 
mony or lead. Tin-plate is only sheet-iron coated with tin. 

Chlorohydric acid dissolves tin with escape of hydrogen, 
forming SnCl. 

Strong nitric acid does not dissolve tin, but the addition 
of a little water to the acid causes a violent action, and the 
tin is speedily converted to stannic acid SnO a . 

597. There are two oxyds of tin : 1. The protoxyd SnO; 
and 2. The peroxyd SnO a . There are numerous intermediate 
oxyds formed of these two. 1. This is obtained by preci- 
pitating a solution of protochlorid of tin with an alkaline 

595. What history is given of tin ? What are its equivalent and general 
properties? 596. Give its density and fusibility? What is said of its 
alloys with copper ? What is tin-plate and pewter ? How does nitric 
acid affect it ? 597. What ozyds of tin are there ? What is the nrot- 




carbonate, which yields a bulky hydrate ot the protoxyd. 
It is a very unstable compound, passing into the peroxyd at 
a very moderate heat. 2. The peroxyd is found native in 
the beautiful crystallized tin stone. It may be obtained in 
a soluble and an insoluble condition. When the perchlorid 
1 is precipitated by an alkali, the bulky white precipitate of 
hydrated peroxyd which appears is easily soluble in acids; 
but if tin is acted on by an excess of moderately strong 
nitric acid, a white insoluble powder is formed, which is 
not acted on by the strongest acids. Heat converts both 
into a lemon-yellow powder, which dissolves in alkalies, but 
not in acids, and which is known as stannic acid : it reddens 
test-paper, and forms salts. The putty used to polish stone 
and glass is the peroxyd of tin 

598. Protochlorid of tin SnCl which is prepared by 
dissolving tin in hot chlorohydric acid, is a powerful de- 
oxydizing agent, and reduces the salts of silver, mercury, 
platinum, &c, to the metallic state. The anhydrous proto- 
chlorid is formed by heating protochlorid of mercury with 
powdered tin. 

599. Perchlorid of tin SnCl a is a dense fuming liquid, 
long known as the fuming liquor of Labavius. It is formed 
by distilling a mixture of 1 part of powdered tin and 5 of 
corrosive sublimate. The tin mordant used by the dyers is 
formed by dissolving tin in chlorohydric acid, with a little 
nitric acid, at a low temperature, or by passing chlorine gas 
through the protochlorid. 

The sulphurets of tin correspond to the chlorids. The 
bisulphuret (aurum musivum) is used as a bronze color for 
imitating gold in ornamental painting and printing, and also 
to excite electricity in the electrical machine, (166.) 

The aichemistic name for this metal was Jove, and the 
medicinal preparations of tin are still called jovial prepa- 


Equivalent, 208. Symbol, Bi. Density, 9*8. 

600. Bismuth is found native, and also in combination with 

Describe the peroxyd. What two modifications of it are named ? How 
does heat affect them ? What is " putty V 598. How is protochlorid of 
tin employed as a reagent? 599. What is perchlorid of tin, and how 
prepared ? What is the tin mordant ? What sulphurets of tin are there t 
What was its aichemistic name ? 




other substances. Native bismuth is found in the United 
States, at Monroe, Conn. It is a brittle, highly crystalline 
metal, of a reddish-white color, with a density of 9*8, and 
fuses at 507°. It is obtained in large and beautiful obtuse 
rhombic crystals, by fusing several pounds of bismuth in an 
earthen pot, purifying by successive portions of nitre, and 
leaving it to cool until a crust is formed on its surface, 
which is pierced by a hot coal and the still fluid interior 
turned out. The vessel will be lined with a multitude of 
brilliant crystals. 

It dissolves in nitric acid, but, like other metals of this 
class, does not decompose water under any circumstances. 

601. Two oxyds of bismuth are known. The protoxyd 
BiO s is formed by gently igniting the subnitrate. It is a 
yellowish powder, easily soluble in acids, and is the base of 
all the salts of bismuth. It is, however, a very feeble base, 
since even water decomposes its salts. The peroxyd Bi0 5 
is not of much interest. 

602. The nitrate of bismuth Bi0 8 .N0 5 + 3HO is the most 
interesting of its salts. It may be obtained from a strong 
solution in large transparent crystals, which are decomposed 
by water. The solution of the nitrate of bismuth turned 
into a large quantity of water is immediately decomposed, 
with the production of a copious white precipitate of subni- 
trate of bismuth. This is owing to the superior basic power 
of the water, which takes a part of the nitric acid. The 
white precipitate is a basic nitrate Bi0 8 .N0 5 -j-3BiO s HO. 
This white oxyd has been much used as a cosmetic. It 
blackens by sulphuretted hydrogen. 

603. The alloy of bismuth, known as Newton's fusible 
metal, is formed of 8 parts bismuth, 5 parts lead, and 3 parts 
tin, and melts at about 208°, (473.) It is much used in 
taking casts of medals. An alloy of 1 lead, 1 tin, and 2 
bismuth, fuses at 200°-75. The expansion of bismuth in 

* cooling renders it a valuable constituent of alloys where 
sharpness of impression in casting is important. 

600. What is the color and fusibility of bismuth ? Describe its crys- 
tals, and the mode of obtaining them. 601. How many oxyds has this 
metal? 602. What is the most interesting property of the nitrate ? What 
use is made of the subnirate ? 603. What its the composition of Newton'* 
foible metal ? What more fusible alloy is named ? 




Equivalent, 129. Symbol, Sb, (Stibium.) Density, 67. 

604. This metal is derived chiefly from its native suU 
phuret, which is a rather abundant mineral. The metal is 
obtained by fusing the sulphuret with iron-filings, or car* 
bonate of potash, which combine with the sulphur and set 
free the metal. It is a white, brilliant metal with a blue 
tint, forming broad rhomboidal crystalline plates in the com- 
mercial article, but fine granular if purified from foreign 
metals, which cause it to assume a coarse crystallization. 
It is very brittle, and, like bismuth, may be reduced to a fine 
powder. It fuses at about 842°, and lower if quite pure : 
a high fusion point is a sign of its impurity. It is, in a cur- 
rent of hydrogen, entirely volatile, but alone and covered 
very slightly so. It dissolves in hot chlorohydric aoid, but 
nitric acid converts it into the insoluble white antimonic 

Its alloy with lead is type-metal, which, like the alloys 
of bismuth, gives very sharp casts, by reason of the expan- 
sion it undergoes at the moment of solidification, which 
forces the metal into all the fine lines of the mould. It is 
remarkable that both of the constituent metals shrink when 
cast separately. Finely powdered antimony is inflamed in 
chlorine gas, forming the perchlorid. 

605. Two oxyds of antimony are known, viz : 

1. Antimonic Oxyd, Sb0 3 . — This oxyd may be obtained 
by digesting the precipitate from chlorid of antimony by 
water, with carbonate of potash or soda, or by burning anti- 
mony in a red-hot crucible ; and also by subliming it from 
the surface of fused antimony in a current of air. It is 
a fawn-colored insoluble powder, anhydrous, and volatile 
when highly heated in a close vessel. Boiled with cream 
of tartar, (acid tartrate of potash,) it forms the well-known % 
tartar emetic, which may be obtained in crystals from the 

The glass of antimony is an impure fused oxyd, pre- 

604. How is antimony obtained? What are its properties? What of 
it* grain ? Its fusion ? Its alloys ? 605. How many compounds does 
antimony form with oxygen ? What important salt does the oxyd form 
wit) totash? 




pared for the purpose of making tartar emetic. Heated 
in air, this oxyd gains another equivalent of oxygen, and 
forms — 

2. Antimonic acid Sb0 5 is formed, as already stated, 
when antimony is digested in an excess of strong nitric acid, 
or better in aqua-regia with nitric acid in excess. It 
dissolves in alkalies, with which it forms definite salts, that 
are again decomposed by acids, hydrate of antimonic acid 
being thrown down. The hydrate loses its water below a 
red heat, becoming a crystalline fawn-colored powder; and 
by a higher heat one equivalent of oxygen is expelled, anti- 
monious acid being formed. 

606. There are chloride and sulphuret* of antimony cor- 
responding to the oxyd and to antimonic acid. 

The tercMorid, butter of antimony, SbCl 8 , is made by 
distilling the residue of the solution of sulphuret of anti- 
mony in strong hydrochloric acid, (fig. 317.) When a drop 
of the distilled liquid forms a copious white precipitate on 
falling into water, the receiver is changed, and the pure 
chlorid is colleoted. It is a highly corrosive fuming fluid, 
and by cooling forms a crystalline deliquescent solid. It is 
used in medicine as a caustic. Water decomposes it, but it 
dissolves in hydrochloric acid unchanged : water poured 
into the solution throws down a bulky precipitate, which is 
a mixture of oxyd and chlorid of antimony, and has long 
been known by the name of powder of algaroth, SbCl 8 . 
2Sb0 8 . 

The bromid of antimony is a crystalline volatile com- 

607. The tersulphuret of antimony SbS 8 constitutes the 
common commercial sulphuret, and the beautiful crystal- 
lized native mineral, antimony glance. 

The pentasulphuret of antimony SbS 5 is formed by boil- 
ing the tersulphuret with potash and sulphur, and throwing 
down the compound in question by an acid, as a golden yel- 
low sulphuret, known by the name of sulphur auratum, 
or golden sulphur of antimony. More generally, however, 
the decomposition on adding an acid, as above, gives us 
the oxysulphuret of antimony SbS s +Sb0 8 , which is a 

What is antimonic acid? 606. Describe the terchlorid? How de- 
decomposed ? 607. What is said of the sulphurets ? What are the golden 
sulphuret and kerme$ mineral t 





characteristic reddish-orange precipitate. This is the sab* 
stance known as kermes mineral, and is an article of the 
older medical practice. The solution of sulphuret of anti- 
mony in caustic potash and sulphur is a case in which 
sulphuret of potassium is a sulphur base, and sulphuret of 
antimony a sulphur acid. 

The formation of tartar emetic with tartaric acid, and 
the production of the characteristic reddish-yellow sulphu- 
ret of antimony with sulphydrio acid are the most signal 
tests of antimony. The sulphydrate of ammonia produces 
the same colored precipitate, but this is soluble in excess of 
the precipitant, as the former also is in the solution of al- 
kalies. The blowpipe also furnishes good evidence : when 
a bit of metallic antimony is fused under the oxyhydrogen 
blowpipe it volatilizes and burns, and if it be thrown on 
the floor or an inclined board, it scatters in numerous burning 
globules, whose path is marked by a white stain of oxyd 
of antimony. We will, under arsenic, mention how anti- 
mony is to be distinguished in cases of poisoning. 


Equivalent, 75. Symbol, As. Density, 5-8. 

608. Metallic arsenic is found native in thick crusts, 
called testaceous arsenic, evidently deposited by sublimation. 
It is, however, more usually obtained in the form of arseni- 
ous acid As0 8 , from roasting the ores of cobalt, nickel, and 
iron, with which metals it is often combined. Mispickel, a 
double sulphuret of iron and arsenic, is a great source for 
this metal. The vapors of arsenious acid given out in the 
roasting are condensed in a long horizontal chimney, or in 
a dome constructed for the purpose ; the first product being 
purified by a second sublimation. Arsenic is a brilliant 
crystalline steel-gray metal, brittle, and easily pulverized. 
In vessels free from air it may be sublimed unchanged at a 
temperature of dull redness. Its vapor is colorless, very 
dense, (10*37,) and has a remarkable odor, resembling garlie. 
The garlic odor is well perceived on subliming a fragment of 

What is the nature of this salt? What are the best tests of antimony? 
How does it act under the blowpipe? 608. How is arsenic found, and 
in what minerals ? What are its properties ? How is it sublimed un- 
changed ? What is the density and odor of its vapor? 





arsenic or of arsenious acid from a live coal. It sublimes 
without fusion. It may, however, be fused in tight vessels 
under pressure of its own vapor. Metallic arsenic soon 
tarnishes in air and assumes a dull cast-iron look. 
It is sold by druggists under the absurd names of 
fly-powder } cobalt, and mercury — names intended 
to deceive and likely to mislead, involving obvious 
danger. Metallic arsenic is easily obtained in distinct 
crystals by subliming the commercial metal, or 
arsenious acid, mingled with charcoal and carbonate 
of soda, or black flux, (484,) in a tube of hard glass, 
or, if a larger quantity is required, in a small retort. 
The mixture is put in a 5, (fig. 380,) and heated to 
redness while the air is shut out. The metal rises 
and is deposited in a black metallic mirror in the cool 
part of the tube just above. Metallic arsenic is an 
active poison. It burns in the air with a blue 
flame, and it is also inflamed in chlorine gas. Fi s- 380 « 

609. The oxyds of arsenic are, 1. Arsenious acid AsO„ 
and 2. Arsenic acid As0 5 . 

1. Arsenious Acid — White Arsenic — Rat J s-bane 9 As0 8 ; 
—This well-known and fearful poison is formed, as just 
stated, when metallic arsenic is sublimed in air, or when 
any of the ores of arsenic are roasted. This oxyd is what is 
usually meant when the term arsenic is used in commerce. 
When newly sublimed, it is a hard transparent glass, brittle, 
and with a density of 3*7. It slowly changes to a white 
opake enamel, resembling porcelain. This change is gradual, 
the vitreous portions being still found in the centre of the 
opake masses. As sold in commerce, it is usually reduced 
to a white powder, rarely* found without adulteration. It 
sublimes at 380°, without change, and crystallizes in bril- 
liant octahedrons, as may be well seen by slowly subliming 
a small quantity in a glass tube. Its vapor is inodorous, 
but if sublimed from charcoal it gives the peculiar garlic 
odor of metallic arsenic, being reduced to that state. It is 
soluble in about 10 parts of hot water, and is almost taste- 
less, with a faint sweetish flavor, which renders it the more 

How may it be fused ? How does air affect it? What names has it? 
How obtained crystallized? 609. What oxyds does it form? Give formu- 
las. What is arsenious acid? What are its common names ? What aro 
its characters? What change does it suffer ? How does it crystallize ? How 
soluble ? What of its taste ? 




dangerous poison, since no warning is given to the victim 
who takes it, as in case of most other metallic poisons. The 
vitreous acid is three times as soluble as the opake. The 
solution in water is acid to test-paper, and deposits nearly 
all its arsenic in crystals on cooling, retaining 1 pari 
to 30 of water. Chlorohydric acid dissolves arsenic, and 
if a solution of 4 parts AsO s in 6 of HCi and 2 of water 
is slowly cooled from boiling, the AsO s is deposited in trans- 
parent octahedrons, and if in the dark, the formation of each 
crystal is accompanied by a spark, and sometimes the light 
produced is such as to illuminate a dark room. The alka- 
lies dissolve arsenic, but do not form crystallizable salts with 
it. Arsenious acid contains As 75-75, O 24-25. 

610. Arsenic Acid, As0 5 . — This acid is formed by adding 
nitric acid to the solution of white arsenic in hydrochloric 
acid, as long as any red vapors of nitrous acid show them- 
selves, and then carefully evaporating the solution to entire 
dryness : a white porous subcrystalline mass remains, which 
is slowly soluble in water. Its solution is a powerful acid, 
quite similar in chemical characters to phosphoric acid. The 
analogy is so great that there is a complete similarity in con- 
stitution, and even in external appearance, between all the 
salts of these two acids. For every tribasic phosphate we 
have an arseniate, not only similar in constitution, but iso- 
morphous, and so resembling it in all its external properties 
as not to be distinguished by the eye. Thus the tribasic 
phosphate of soda (512) and the tribasic arseniate of soda, 
are — 

Phosphate of soda H02NaO.PO,-r-24Aq. 

Arseniate of soda H02NaO.AsO,-f-24Aq. 

These, and many other facts, lead to the opinion that the 
elements are themselves isomorphous; and in fact arsenic has 
no claim to the metallic character but its lustre, being in 
chemical properties and natural affinities associated with 

611. The chlorid of arsenic AsCl 8 is a fuming volatile 
liquid, decomposed by water, and very poisonous. The 
bromid and iodid are both crystallizable solids, also decom- 
posed by water. 

What is said of its chlorohydric solution ? 610. How is AsOi formed? 
What are its properties? What analogy has it with PO»? To what 
opinion do these facts lead ? 611. What of chlorid of arsenic ? 

. Digitized 



The sulphurets of arsenic are natural compounds, used an 
pigments, and also in pyrotechny. The first, AsS 2 , is a red 
transparent body, called realgar, and AsS 2 is the golden- 
yellow orpiment Both these substances are found native, 
and are usually associated. They are brought from Koor- 
distan in Persia, and from China. The Mohammedans use 
the yellow orpiment as a depilatory in their ceremonial puri- 
fications. Two higher sulphurets may be formed, which aie 
As0 5 and AsO- : the former is the product thrown down 
by sulphuretted hydrogen in a solution of arsenic. The 
sulphurets are soluble in alkalies and in sulphydrate of am- 

612. Arseniuretted Hydrogen, AsH 8 . — This is a gas pro- 
duced by the action of dilute sulphuric acid on an alloy of 
line and arsenic, or by the evolution of hydrogen in presence 
of arsenic or arsenious acid. 
Figure 381 shows the ordinary 
gas evolution bottle A, in which 
are the materials for producing 
hydrogen. An arsenical solution 
poured in at n m, immediately 
changes the color of the flame 
at 6; before colorless, it now 
becomes of a peculiar blue, and 
evolves a cloud of arsenious acid, Fig. 381. 

or deposits metallic arsenic on a cold surface. Marsh's test 
for arsenic depends on the generation of this gas. It is a 
virulent poison of the most active description. This gas is 
readily absorbed by a solution of sulphate of copper, and 
precipitates an arseniuret of that metal. Its density is 2*69 : 
it has a peculiar disgusting odor, and is decomposed by heat 
alone with deposition of metallic arsenic. It is liquid at 
— 22°F. : water dissolves it slightly, and chlorine completely 
decomposes it with flame. 

Detection of Arsenic in Poisoning. 

613. The too frequent use of arsenic as a means of destroy- 
ing human life renders it of the greatest moment to know 
certain processes for its detection. Arsenic is almost always 

What are the sulphurets ? 612. What is arseniuretted hydrogen ? Ea* 
produced? What of its flame? What are its properties? 613. What 
of arsenical poisoning ? 




fatal when it has time to become absorbed by the circulation 
in sufficient quantity. The most reliable antidotes which 
have been proposed are the moist hydrates of sesquioxyd 
of iron and of caustic magnesia. With both these arsenic 
forms insoluble salts. The alkalies, being solvents of arsenic, 
only increase the danger by favoring absorption. 

We enumerate a few of the tests for arsenious and arsenic 

1. Sulphydric acid produces in acid or neutral solutions 
of As0 8 and As0 5 a rich orange-yellow precipitate, (orpi- 
ment,) soluble in ammonia and alkalies, and in sulphydrate 
of ammonia, but precipitated again by acids. 

2. Nitrate of silver and ammonia-nitrate of silver pro- 
duce in solutions of arsenious acid a lemon-yellow precipitate, 
(arsenite of silver,) soluble in nitric acid. In solutions of 
arsenic acid they produce a brick-red precipitate. 

3. Ammonio-svlphate of copper gives a brilliant green 
precipitate (Scheele's green) in alkaline or neutral solutions of 
arsenious acid, which precipitate (arsenite of copper) is soluble 
in excess of ammonia. 

4. A slip of bright metallic copper, placed in a boiling 
solution of arsenic or arsenious acid made acid by chloro- 
hydric acid, is soon coated with a gray deposit of metallic 
arsenic. This is called Reinsch's test, and is applicable even 
in presence of organic matters which vitiate, partially or 
wholly, the previous tests. 

5. Reduction of the metal from the oxyds or sulphurets 
is justly esteemed in judicial investigations as the most reli- 
able of all* tests. This is accomplished by several modes. 

^ The oxyds or sulphurets are mra- 

4* gled with finely-powdered charcoal 

and carbonate of soda or cyanid 

of potassium and placed in a small 

tube a d (fig. 382) of hard glow. 

The part a b is heated red hot, 

Fig. 382. when, if arsenic is present, it is 

sublimed in a black metallic mirror at c. A small tube is 

used, because in many cases very minute portions are opo- 

What are antidotes, and why? How does sulphydric acid act as a test 
of arsenic ? How nitrate of silver and ammonia ? How ammonia-sul- 
phate of copper? What is Reinsch's test? What of the reduction pre- 
ferred? Describe from fig. 382. 





Fig. 383. 

rated on. In order to prove the character of this ring, the 

tube is broken off at b y (fig. 383,) and the 

flame of a spirit-lamp applied cautiously 

while the tube is gently inclined. A 

current of air passing over the ring of 

metal converts it to arsenious acid, which 

lines the cooler parts of the tube with 

small brilliant octahedrons of a size 

visible by a magnifier. If further proof 

were required, a current of sulphydric 

acid will convert the white crust into yellow orpiment, 

wholly soluble in ammonia, precipitated by chlorohydrio 

acid, and insoluble in that menstruum. 

6. Marsh's test, by means of arseniuretted hydrogen, gives 
unequivocal testimony when arsenic is present Fig. 384 
shows a convenient form of the apparatus used 
for this purpose, which is more simply arranged 
as in fig. 381. This apparatus has the conve- 
nience of a cock to regulate the escape of the 
gas. The zinc is in the lower bulb— the acid 
water and suspected substance are introduced 
by the upper bulb. The zinc and all the 
materials employed must be scrupulously ex- 
amined as to freedom from arsenic. For this 
purpose the flame of hydrogen must not give the 
least spot upon clean porcelain. On adding 
the arsenical solution, however, the flame be- 
comes livid, larger, gives off white vapors, and 
deposits a tache or spot, in the form of brown- Fifr 88 * # 
black mirror, on the surface of porcelain, as in fig. 385. 
Antimony gives a similar spot, which is liable to be con- 
founded with that from arsenic. It is, however, more sooty- 
black. Exposed to vapor of iodine in a small capsule, anti- 
mony spots turn reddish orange, while arsenic spots appear 
orange yellow, and soon vanish entirely. Exposed for a 
moment to vapor of chlorine given off from bleaching-pow- 
ders in a capsule, the spots being on the underside of the 
cover of the same, the spots disappear. If a drop of nitrate 
of silver be then let fall on the flat surface, if arsenic was 

How is it oxydised in fig. 383 ? What further proof may be had ? What 
is Marsh's test ? Describe fig. 384. What care is required ? What effect 
Is seen on introducing an arsenic solution ? What gives a similar spot ? 
How are the spots distinguished ? How by chlorine and nitrate of silver I 





present there will be a brick-red stain visible, amounting to 
a precipitate if much of the metal existed — while antimony 
does no such thing. These distinctions are conclusive. 

The arrangement of Marsh's apparatus recommended by 
the commission of the Paris Academy, in cases of judicial 
investigation, is shown in fig. 385. The evolution bottle A 

Fig. 385. 

is provided with a bulb-tube a b, to retain moisture, which is 
more effectually removed by the chlorid of calcium tube c d. 
The gas is conducted through the horizontal tube / g, ter- 
minating in a jet-point, where the tache of the flame can be 
received upon a clean porcelain surface C. As heat decom- 
poses the arseniuretted hydrogen, means are provided to 
heat the tube while the gas is passing, the radiant heat 
being cut off by a screen c. In this case the metallic arsenic 
appears in a ring at /, while the flame loses its peculiar 
character, and no tache is seen at g. The ring so obtained 
may be subsequently tested as before indicated, as well also 
as the tache. The cause of the tache will appear on a 
moment's attention. Calling to mind what was said on the 
structure of flame, (460,) it is obvious, by reference to fig. 

386, showing a larger view 
. the part a' c must contain 
- the reduced arsenic in hot 
hydrogen gas, surrounded 
by the burning envelope 
a c b. Now the porcelain 
surface is held in the line 

Fig. 386. 

Describe fig. 385. What does the heat accomplish ? How is the tache 
tbtained in fig. 385 ? 




t x, and must receive the metallic mirror, if any arsenic is 

614. In most cases of arsenical poisoning it is required 
to search for proof in the mass of organic matters ejected by 
the patient, or in the tissues of the body itself; and either 
case requires all organic matters to be destroyed before tests 
can be applied. This may be done in a great majority of 
cases by oxydizing and charring the whole mass to be treated, 
cut small, in a porcelain capsule, with a mixture of strong 
nitric acid and oil of vitriol. These are added in small 
quantity, and gentle heat applied until the coaly mass is nearly 
dry. Water is then added, and the whole thrown upon a filter 
and washed : the filtrate contains all the arsenic and other 
metals. Marsh's, Reinsch's, or any of the other tests just 
enumerated may then be applied. Such is a very brief ac- 
count of the most valuable modes of examination in cases of 
poisoning by arsenic. Further details would be out of 
place here. 



Equivalent, 100. Symbol, Hg, (Hydrargyrum?) Density, 

615. This is the only metal which is fluid at ordinary 
temperatures. It is found as native, or running mercury, in 
Spain and Carniola, and also as cinnabar, or sulphuret of 
mercury. In Upper California a very large deposite of cin- 
nabar has lately been opened. It is also found both in Mexico 
and Peru. The alchemists supposed it to be silver enchant- 
ed, (quicksilver,) and made many efforts to obtain from it 
the solid silver it was supposed to contain. 

Pure mercury is a silver-white, fluid metal, unchanged by 
air, and very brilliant. Cooled below — 3944°, as by car- 
bonic acid, (150,) it solidifies, and is then as malleable as 
lead. It crystallizes in cubes. It boils at 662°, and forms 
a colorless vapor, of the density 6-976. Even at 32°, a 

614. How is proof obtained in case of organic matters being present ? 
What agent of oxydation is used ? How is the testing carried on ? What 
are noble metals? 615. What of mercury? How found? Why called 
quicksilver ? What are its propertief ? 




very rare vapor rises from it, as is evident from the effect 
on daguerrian plates. If heated in the air at or above 600°, 
it slowly passes to the condition of red oxyd of mercury, 
which is its highest combination with oxygen. By this ex- 
periment Lavoisier proved the composition of air, and per- 
formed the first recorded chemical analysis. 

616. The uses of mercury are numerous and important in 
the arts, and also in medicine. It forms alloys (amalgams) 
with many other metals ; with tin it constitutes the brilliant 
coating of glass mirrors, (called silvering,) and it is of indis- 
pensable importance in procuring gold and silver from their 
ores, and in gilding by the old process. Its use in filling 
thermometers and barometers has already been noticed. It 
expands by each degree of Fahr. 2 ^ TTJ of its bulk, in heat- 
ing from 32° to 212°, and at nearly the same ratio for the 
whole scale of 662°. 

617. The purity of mercury is roughly judged of by its 
forming no film on glass, and by its breaking into small 
globules, which should preserve their spherical form, when 
they run from an inclined surface. If they form a queue, or 
drag a tail, as the workmen express it, it is owing to the 
presence of lead or some other similar impurity. 

It may be purified from all non-volatile ingredients by 

Fig. 387. 

distillation in an iron bottle A, (fig. 387,) formed of one of 
the iron flasks in which quicksilver is imported. This is 

What of its volatility? 616. What are its uses? What fits it spe- 
cially for thermometers ? What is its rate of expansion ? 617. Btow if 
Its purity judged of ? How is it purified ? Describe fig. 387. 




completely enclosed in the furnace, and the tnbe b c con- 
nects with a bag of leather or caoutchouc, reaching to a basin 
of water, and kept cool by a stream of water from the cock 
r. The tension of its vapor is very small, so that it quickly 
returns to the fluid state, thus producing a great commotion 
in the process of boiling. The distilled mercury is only 
partly purified, and the process must be completed by the 
action of dilute nitric acid at a gentle heat, which unites to 
form nitrate of mercury with a part of the mercury. This 
salt reacts with the other portion of the mercury to form 
nitrates of all other metals which may be present. After a 
day or two, with frequent agitation, the action is complete, 
the water is evaporated at a gentle heat, and the crust of 
nitrate of mercury removed. The remaining mercury, now 
quite pure, is washed with much water and dried. 

Mercury may be so finely divided by agitation and other 
mechanical means, as to lose its metallic appearance entirely, 
as in blue pill, mercurialized chalk, (creta cum hydrargyro,) 
and mercurial ointment, which do not, as has sometimes 
been stated, contain the suboxyd of mercury, but only 
mercury in a state of very minute meohanical division. 

Nitric acid dissolves mercury very rapidly even in the 
cold : hydrochloric acid scarcely acts on it, and sulphurio 
only by the aid of heat, when it forms an insoluble sul- 
phate of mercury, evolving sulphurous acid. The equiva- 
lent of mercury is often stated at 200, on the supposition 
that the gray oxyd is the protoxyd ; but this seems to be 
more properly considered as a suboxyd, and the real pro- 
toxyd as the red oxyd. On this view the equivalent is 
stated at 100. 

618. The gray, or suboxyd of mercury, Hg a O, is formed 
by digesting calomel in caustic potash, or by adding the 
same reagent to a solution of the nitrate of the suboxyd of 
mercury. It is an insoluble, dark gray powder, which is 
easily decomposed into metallic mercury and the red oxyd, 
Hg 9 = HgO+Hg. 

The red oxyd, or 'protoxyd, red "precipitate, HgO, is 
prepared in the large way by heating the nitrate very cau- 
tiously until it is quite decomposed, and a brilliant red 

How is the purification completed ? How does mechanical action af- 
fect it? Give examples. What dissolves it? How does SO, affect it? 
What of its equivalent ? 618. How is suboxyd formed ? How decom- 
posed ? How is the red oxyd formed ? What is precipitate per $e t 




crystalline powder produced. It may also be formed by 
heating metallic mercury for a long time in a glass vessel 
nearly closed, and in this form is the preparation to which 
the old name of red precipitate per se was applied. Heat 
decomposes this oxyd, into oxygen and metallic mercury. 
It is, like the oxyd of lead, slightly soluble in water, and 
gives to it an alkaline reaction. It is a poison, and is used 
externally as an irritant and escharotic. 

619. The cMorids of mercury correspond to the oxyds, 
and are both very important compounds. 

1. Subchhrid of Mercury, (Calomel,) Hg 3 CL— This well- 
known medicine is formed by precipitating a solution of sub- 
nitrate of mercury with common salt. A white, insoluble, taste- 
less powder falls, which is the calomel. Even strong acids, 
when cold, do not affect it ; but it is instantly decomposed 
by alkalies, and the suboxyd produced. Heat sublimes it 
unchanged. Its complete insolubility at once distinguishes 
this safe and mild substance from the highly poisonous 
corrosive sublimate. It should be in very tine powder for 
medical use, as then the presence of corrosive sublimate is 
easily detected in it by imparting its taste to water. Its 
freedom from adulteration may be determined by heating it 
on the surface of a clean spatula, when it should volatilize 
unchanged without leaving any residue. It is obtained by 
slow sublimation, in beautiful transparent crystals — square 
prisms with octahedral summits. Its density is 6*5, and in 
vapor 8*2. Vapor of calomel is composed of 

1 volume of mercury vapor. 6*976 

£ volume of chlorine. 1*220 

1 volume of calomel vapor.. Hg*Cl 8*196 

Calomel is decomposed by nitric acid, forming corrosive 
sublimate and nitrate of protoxyd of mercury. Ammonia 
turns it to a gray powder, which is an amid and chlorid of 
mercury Hg^Cl.HgNH,. 

2. Corrosive Sublimate, or Chlorid of Mercury, HgCl. 
— This salt is most economically prepared by the decompo- 
sition of sulphate of mercury, by common salt, whose 

How does heat affect it ? How is it used ? 619. What of the chlo- 
rids? What is the name of the subchlorid ? How formed ? What are its 
properties ? What of its state and purity ? Its density ? What is the 
constitution of its vapor? What decomposes it ? What is corrosive 
t ublimate ? 




simple interchange gives corrosive sublimate and sulphate 
of soda, HgO.S0 3 +NaGl = HgCl+NaO.S0 8 . The chlo* 
rid is also formed by dissolving the red precipitate in hot 
chlorohydric acid. Corrosive sublimate is a very heavy 
crystalline body, soluble in about 16 parts of cold water, 
and in two or three parts of hot, giving a solution which 
possesses the most distressing and nauseous metallic taste, 
and is a deadly poison. It is soluble in alcohol and ether. 
It melts at 509° and sublimes at about 563°. Its vapor 
has a density of 9*42, and contains 

1 volume of vapor of mercury '.. 6*967 

1 volume of chlorine 2*440 

1 volume HgCl 9*407 

Albumen completely precipitates it, and the whites of 
eggs or milk are therefore antidotes for this poison. For the 
same reason it is, doubtless, that timber and animal sub- 
stances are preserved from decay, as in the hyanizing pro- 
cess, by steeping in solution of corrosive sublimate. The 
albuminous portions of wood suffer decay sooner than the 
vegetable fibre, and these are rendered completely inde- 
structible in the process of. Mr. Kyan, which is now in use 
in our national shipyards. 

Ammonia produces in solution of corrosive sublimate (and 
also in those of other salts of protoxyd of mercury) a 
white bulky precipitate of uncertain composition, and long 
known as white precipitate. It is regarded as a double amid 
and chlorid of mercury Hg fl Cl.NH g . 

620. There are two iodids of mercury, Hg a I and Hgl. 
— The second is a brilliant scarlet-red precipitate, formed 
by adding solution of iodid of potassium or hydriodic acid 
to a solution of corrosive sublimate. The iodid is at first 
yellow, but soon passes by molecular change into the splen- 
did scarlet crystalline powder before noticed. It cannot be 
used as a pigment on account of its instability. 

Two stdphurets of mercury exist Hg g S and HgS, the first 
of which is a black powder, formed when sulphuretted hy- 
drogen is passed through a solution of subnitrate of mercury. 
The sulphuret HgS, or cinnabar, is formed when the nitrate 

How procured ? Give the formula. Give its properties. What is the 
density of its vapor? What is an antidote for it ? What is kyanizing? 
What is white precipitate ? 620. What iodids of mercury are there t 




of mercury (nitrate of the red oxyd) is treated with sulphu- 
retted hydrogen. It is a black precipitate, but turns red 
when sublimed, and forms the familiar pigment, vermillion. 
This is the common ore of the quicksilver mines. 

Salts of Mercury. 

621. The salts of protoxyd of mercury HgO are colorless, 
but the basic salts are yellow. 

The Nitrates of Mercury. — The action of nitric acid on 
mercury varies with the temperature and the strength of the 
acid. In the cold, dilute nitrio acid dissolves mercury, 
forming a neutral nitrate of the suboxyd ; but if the mercury 
is in excess, a salt is deposited in large and transparent white 
crystals, which is a nitrate with excess of base. If hot and 
strong, the nitrate of the red oxyd is formed, which is a very 
soluble salt, not crystallizable. A basic salt of this oxyd 
may also be formed, which is decomposed by water. 

Sulphate of mercury HgO. SO, results as an insoluble 
white subcrystalline powder, by the action of the strong acid 
on metallic mercury, sulphurous acid being evolved. Boil- 
ing water decomposes this salt, removing a part of its acid, 
by which a yellow basic sulphate is formed, known as tur- 
peth mineral. Its composition is 3HeO.SO a . The sulphate 
of the gray oxyd Hg a O.SO, is formed as a crystalline white 
powder, by treating a solution of subnitrate of mercury with 
sulphuric acid. It is slightly soluble in water. Fulminat- 
ing mercury and other cyanids are described in the organic 

All the compounds of mercury are volatile at a red heat; 
and those which are soluble whiten a slip of clean copper, 
by depositing metallic mercury on its surface. 


Equivalent, 108. Symbol, Ag. (Argentum.) Density, 10 # 5. 

622. The mines of Mexico and of the Southern Andes 
furnish most of the silver of commerce, although many mines 
of this metal are found in Spain, Saxony, and the Harts 
Mountains. Galena, or the native sulphuret of lead, is also 

What is vermilion? 621. How are the nitrates of mercury obtained? 
What is the nature of the nitrate of the red oxyd ? How is the sulphate 
formed ? What are the characteristics of mercurial compounds ? 622. 
From what sources is silver obtained ? 



SILVER. 867 

a constant source of silver, as it is never quite free from this 
precious metal. Silver is often found native. It is more 
usually in combination with sulphur and antimony. 

The brilliant lustre and white color of this valuable metal 
are familiar to all. It is perfectly ductile and malleable, and 
in hardness stands between gold and copper. For the pur- 
poses of economy and in coinage it is essential to alloy it 
with about T ^ part of copper, to render it sufficiently stiff 
and hard. It is one of the best conductors of heat and 
electricity, and its surface reflects light and heat more per- 
fectly than any other metal. It is used for this reason in 
reflectors ; and hot fluids longer retain their heat in vessels 
of silver than in any other. It remains untarnished in air free 
from sulphur gases ; from these it gains a brown-black sur- 
face of sulphuret of silver. It does not combine with oxygen 
when heated in it ; but fused silver absorbs even twenty times 
its volume of oxygen, parting with it again on cooling. It 
is slightly volatile even in the furnace, but in the carbon 
crucible of the galvanic focus (fig. 169) it volatilizes com- 
pletely. It crystallizes in cubes often very beautifully 
modified. It fuses at 1873° ; and, owing to its absorption 
of oxygen and disposition to contract in the mould, it is a 
difficult metal to cast. Nitric acid dissolves silver in the 
cold with great rapidity, and if it contains any gold, this is 
left undissolved as a brown powder. Solution of coin alloy 
appears green, from the copper it contains. Hydrochloric 
acid scarcely acts on silver, and sulphuric acid only when 
hot, forming the sparingly soluble sulphate. 

Silver is obtained pure from its solution in nitrio acid by 
precipitation with metallic copper, as a finely-divided crys- 
talline powder ; also by decomposing its chlorid by fusion 
with two parts of dry carbonate of potash. 

623. Silver is parted from alloys of copper and from argen- 
tiferous lead by the process of cupellation. This depends on 
the oxydation of the base metal in a 
current of heated air, and the absorption 
of these oxyds by the cupel. This is 

made of bone-ashes, and compacted in a 

mould into the form of fig. 388 ; seen in Fig. 388. 

What are the properties of silver ? What does fused silver absorb ? 
How volatile ? What of coin ? What dissolves it ? What separates mo- 
tallic silver from its solution ? 623. What is cupellation ? Describe the 





section in fix. 889. The bone-ash does not fuse at the most 
intense heat of the cupellation furnace. The 
s t*r cupels are of various sizes, according to the weight 
wzzzzf of the assay. In metallurgic art they are employed 
Fig. 389. in the final purification of silver-lead, of immense 
size, constructed on a hearth of bricks. Those here figured 
are small, and are heated in a muffle, or low oven-shaped ves- 
sel, (fig. 390,) set in the cupellation furnace, 
i as shown in section A, (fig. 392.) Several 
cupels are accommodated on its hearth, 
Fig. 390. while the air entering its mouth D, partly 
closed by E, draws over the surface of the fused assay, and 
out at the lateral slits A in the muffle, thus oxydizing the 

Fig. 391. Fig. 392. 

lead. Fig. 391 is a general view of the cupellation furnace, 
which is formed of three parts, united where the bands are 
shown. The sectional drawing (fig. 392) indicates more 
clearly the relations of the parts. Small charcoal is fed to 
the fire Gr at F, and the ignited coal finds its way to B, where 
it rests on the hearth K. To aid this descent, an iron rod 

What is the muffle ? Describe the process and figs. 391 and 392. 



SILVER. 369 

is introduced from time to time at o 0, (fig. 391.) The 
opening I H regulates the draft, which is suspended by open- 
ing F G. The muffle is thus heated very intensely, and the 
condition of the assay is observed from time to time by re- 
moving E. M is the draft-pipe, and N a sheet-iron shelf to 
receive the hot cupels. Pure metallic lead is usually added 
to the alloy to be cupelled, to several times its weight. The 
oxyd of lead is absorbed as fast as it is formed, carrying 
with it oxyd of copper and other impurities into the porous 
bone-ash. Finally, at the close of the process, the globule 
of silver flashes into a perfectly polished sphere or button 
of a white color. This is one of the most ancient and valu- 
able of metallurgical operations, and is equally applicable 
to gold and its alloys as to silver. By this process all the 
currency of the world is regulated, — in connection with the 
process of solution in nitric acid, and precipitation by a stand- 
ard solution of salt, which is known as Gay-Lussac's wet 
assay in distinction from cupellation, which is called the dry 

624. Much of the lead of commerce contains too little silver 
to allow an economical use of the process of cupellation . The 
silver is then separated by Pattinson's process, as it is called, 
founded on the fact that the alloy of silver and lead is more 
fusiUe than pure lead; and the latter, on cooling, separates 
in small crystals, which can be skimmed out of the richer lead 
by an iron cullender. This process enables the metallurgist 
to remove with profit even so small a proportion as six ounces 
of silver from a ton of lead. The small portion of rich lead 
is then cupelled. 

625. Three oxyds of silver are known by chemists : the 
snboxyd Ag 9 j the protoxyd AgO; and the peroxyd AgO fl . 
We will now notice only the protoxyd. This is formed 
when the solution of silver in nitric acid is saturated with 
caustic potash, or when the chlorid of silver, recently pre- 
cipitated, is digested in a solution of caustic potash of den- 
sity 1/3. It is a dark-brown or black powder, if prepared 
by the first mode, or quite black and dense by the second 
process. It is a base, forming well-defined salts. Ammonia 

How does the button appear at the consummation of the process? 
What is the wet and what the dry assay ? 624. What is Pattinson's pro- 
•oss? 625. What oxyds of silver are there? How is AgO formed? 
What are its properties ? 





dissolves it readily, and it is also somewhat soluble in water, 
to which it gives an alkaline reaction. The solution of oxyd 
of silver in cyanid of potassium forms the silver-plating so* 
lution in this branch of electro-plating. The oxyd is easily 
reduced by heat alone, and by the contact of organic matter. 
626. Chlorid 0/ silver AgOl is formed -when any soluble 
salt of silver is treated with a soluble chlorid or with chlo- 
rohydric acid. This substance fuses at a moderate red 
heat into a transparent pale-yellow fluid, which is horny and 
tough when solid, and hence called horn silver, a form in 
which this metal is sometimes found in mines. It is very ^ 
sensitive to light, turning dark and finally black, especially 
in contact with organic matter in sunlight. It is easily 
reduced to the metallic state by the nascent hydrogen gene- 
rated when zinc is acted on by dilute sulphuric acid in con- 
tact with the chlorid. Pure silver and chlorid of zinc result ; 
or it may be reduced by fusion with twice its weight of car- 
bonate of soda or potash, (622.) 

The iodid and bromid of silver are, like the chlorid, inso- 
luble in water, and very sensitive to light. The daguerreo- 
type and calotype are both dependent on the sensitiveness 
of these compounds to light, for the accuracy and beauty 
of their results. 

The sulphurets of silver are found native, and the tarnish 
which blackens silver articles on long exposure, is formed 
by sulphuretted hydrogen in the air. 

627. The nitrate 0/ silver AgO.N0 5 is a salt which crys- 
tallizes in beautiful flattened tables of an hexagonal form, 
soluble in half their weight of hot water. By heat it fuses, 
and, when cast in cylindrical moulds, forms the slender 
sticks called lunar caustic, so much used by the surgeon. 
Its solution has a disgusting metallic taste, even when very 
dilute. It is a most delicate test of the presence of chlorine 
or of any of its compounds. It blackens rapidly in contact 
with organic matter when exposed to the light, and forms 
an indelible ink, which is much used in marking linen. 
Solution of cyanid of potassium will remove the stain pro- 
duced by nitrate of silver. Metallic copper at once throws 
down metallic silver from the nitrate, and solution of nitrate 

626. Describe the chlorid. How can it be reduced? What are the 
relations of the silver compounds to light? What is the action of sul- 
phuretted hydrogen on silver ? 627. Describe the nitrate. What is lunar 
caustic ? What are its reactions ? 



GOLD. 37i 

of copper is formed. Mercury precipitates metallic silver 
from * dilute solution, in beautiful tree-like forms, called 
cvrbor Diance. Ammonia, by acting on precipitated oxyd 
of silver, forms a fulminating compound. It is extremely 
hazardous to deal with, as it explodes even when wet. 

The fulminating silver produced by the reaction of alco- 
hol, nitric acid, and silver, will be described in the Organic 


Equivalent, 98'7. Symbol, Au. Density, 19-26. 

628. This valuable metal is found only in the metallic or 
native state, being very widely diffused in small quantities 
in the older rocks. From these, by the action of various 
causes, it finds its way into the sand of rivers, and is dis- 
tributed in small quantities, in many widespread deposits 
of coarse gravel or shingle, as in Alta California, Australia, 
on the eastern flanks of the Ural mountains, and over a wide 
belt of country in Virginia, the Carolinas, Georgia, and Ala- 
bama. These diluvial deposits furnish nearly all the gold 
of commerce, by the process of washing and amalgamation 
with mercury. Large masses of gold sometimes occur, as 
one of twenty-eight pounds in North Carolina. In Si- 
beria a mass was found, now in the Imperial Cabinet of St. 
Petersburg, weighing nearly eighty English pounds. Several 
of still greater • size, mingled with quartz, have been found 
in California. Generally, however, it occurs only in minute 
rounded and flattened grains or scales. It is also found in 
veins of quartz, in compact limestone, and distributed in 
iron pyrites. Native gold is usually alloyed with from 5 
to 15 per cent, of silver. Since the discovery of gold in 
California, in March 1847, it is estimated that at least fifty 
millions of dollars have been annually obtained there, chiefly 
from the auriferous sands of those regions. 

629. Gold is distinguished by its splendid yellow color, 
its brilliancy, and freedom from oxidation, by its extreme 
malleability and ductility, by its high specific gravity, (19-26 
to 19*5,) and by its indifference to nearly all reagents. It 

What is the arbor Diance t 628. How does gold occur in nature ? How 
ii il obtained? What of California? 629. Describe this metal ? 




fuses at 2016° F., and is dissolved only by aqua regia, 
(420,) chlorine, nascent cyanogen, and by selenic acid. The 
first is the solvent commonly known, and yields perchlorid 
of gold. 

630. Gold forms two very unstable oiyds, Au a O and 
Au t O,, which are decomposed even by light. Two corre- 
sponding chlorids exist. The perchlorid is a very deliques- 
cent salt, forming a red crystalline mass, soluble in ether, 
alcohol, and water. Metallic gold is deposited in elegant 
crystalline crusts from the ethereal solution of the cblorid. 
Ammonia throws down from solutions of gold an olive- 
brown powder, fulminating gold, which, when dry, explodes 
with heat, or by percussion. 

631. The solution of protosulphate of iron throws down 
gold from its solutions in a very fine brown powder, which, 
wben diffused in water, is green, as seen by transmitted light. 
The protochlorid of tin forms a characteristic purple preci- 
pitate in gold solution, called the purple of Cassius, whicb 
is used in porcelain-painting, and is probably a compound 
of the oxyds of tin and gold. Gilding of ornamental work 
is usually performed by gold-leaf; but other metals are 
gilded, either by applying it as an amalgam with mercury, 
the mercury being afterward expelled by heat, or preferably 
by the new process of galvanic gilding from a solution of the 
double cyanid of gold and potassium. Gold wash, as it is 
called, is applied by a mixture of carbonate of soda or potash 
in excess, with oxyd of gold, in which small articles cleansed 
in nitric acid are boiled, and thus become perfectly covered 
with a very thin film of gold. 

632. Palladium, Pd. — This very rare metal is usually as- 
sociated with gold, being found in a native alloy of gold and 
silver from Brazil. It is a white metal, more brilliant than 
platinum, very infusible, malleable, and ductile. It is, how- 
ever, fused by the compound blowpipe. It gains a blue 
tarnish, like steel, by heating in the air, which it loses by a 
white heat. In hardness it is equal to fine steel, and it does 
not lose its elasticity and stiffness by a red heat. Its density 
varies from 10*5 to 11-8. It suffers no change by exposure 

What is its usual solvent ? 630. How many oxyds of gold are there f 
Describe the perchlorid. 631. What tests distinguish gold? How if 
gilding effected ? 632. What of palladium ? What peculiar properties 
Us it? 




in tbe air. It gives a peculiar and beautiful color to tbe 
surface of brass wben applied in tbe electro-metallurgical 
process. Its equivalent is 53-3. Its qualities would 
render it a very valuable metal if it could be obtained in a 
sufficient quantity. Nitric acid dissolves it slowly, but aqua 
regia more rapidly. It forms two oxyds and two correspond- 
ing cblorids. 


Equivalent, 98*7. Symbol, PL Density, 19*70 to 21-23. 

633. Platinum Is ai very remarkable metal, and, if abun- 
dant, would be extensively useful in domestic economy. It 
' is found native in tbe gold-workings in Soutb America, and 
in Siberia on the eastern slope of the Urals. No ore of 
platinum is known except its alloy with gold, and those 
with iridium, osmium, and rhodium. 

Platinum is a white metal, between tin and steel in color, 
but harder than gold or silver, and, unless quite pure, is, 
when unannealed, nearly as hard as palladium. A very 
little rhodium or iridium renders it more gray in color and 
much harder. If pure it is very malleable, especially when 
hot, and can then be imperfectly welded. Its ductility and 
tenacity are remarkable ; but its most valuable property is 
its infusibility, which is so great that the thinnest platinum 
foil may be safely exposed to the most intense heat of a 
wind furnace. It is soluble only by aqua regia. It alloys 
readily with lead, iron, and other base metals, so that great 
care is needed in using platinum vessels, not to heat them in 
contact with any metal or metallic oxyd with which they 
combine. Caustic potash, and phosphoric acid, in contact with 
carbon, will also act upon platinum at a red heat. This 
is a most useful metal to the chemist, and vessels of plati- 
num are quite indispensable in the operations of analysis. 
Large retorts or boilers are made of it for the use of manu- 
facturers of sulphuric acid, holding sometimes sixty or 
more gallons. In Russia it has been employed in coinage, 
for which by its great density and hardness it is well suited. 
When recently fused by the compound blowpipe or the gal- 

633. What is the history of platinum ? Describe its characters and 
uses ? What of its density ? 





vanic focus, its density is about 19 -9, which is increased to 
21*5 by pressure and heat. 

634. Platinum is obtained pure by digesting crude plati- 
num in aqua regia, and adding to the deep- 
brown liquid a solution of chlorid of ammo- 
nium : this throws down an orange-colored 
precipitate, which is a double chlorid of plati- 
num and ammonium. This precipitate is 
reduced by heat to the metallic state, — a 
porous dull-brown mass, commonly known as 
platinum sponge. All the platinum of com- 
merce is treated in this way. The sponge is 
condensed in steel moulds, like fig. 393, by heat 
and pressure, and when compact enough to bear 
the blows of the hammer, is heated and forged 
until it is perfectly tough and homogeneous. 
The follower K is driven down by the hammer 
upon the platinum sponge confined in the steel 
seat c b. 

I Spongy platinum is a very remarkable sub- 
'* stance, having, as already noticed, (409,) power 

Fig. 393. tQ cause the combination of hydrogen and 
oxygen, and to effect other chemical changes without being 
itself altered. 

Platinum black is a still more curious form of this metal. 
It is formed by electrolyzing a weak solution of chlorid of 
platinum, when the black powder appears on the negative 
electrode. The silver plates in Smee's battery (192) are 
prepared in this way. It is also prepared by adding an 
excess of carbonate of soda, with sugar, to a solution of 
chlorid of platinum, and gradually heating the mixture to 
near 212°, stirring it meanwhile. The black powder which 
falls is afterward collected and dried. This powder has 
the property of causing union among gaseous bodies — as, 
for example, the elements of water — to a greater degree 
than the spongy platinum. 

635. Platinum forms two oxyds, and two chlorids, vis. 
PIO; P10 a and P1C1; P1C1,. The oxyds are prepared from 
the chlorids by precipitation with alkalies, and are very 

634. How is it obtained from its ores ? How is it condensed ? What 
Is platinum black, and what are its properties ? 635. How is tho bi- 
ehlorid prepared ? 



osmium. 376 

unstable. The protochlorid is prepared by heating the 
bichlorid to 460°, when chlorine is evolved and P1C1 is 
left as a greenish-gray insoluble powder. 

The bichlorid of platinum is the usual soluble form of 
platinum, and is always formed when platinum is digested 
in aqua regia. It is prepared pure by dissolving spongy 
platinum in this menstruum, and cautiously expelling the 
acid by evaporation, at the temperature of a water-bath. It 
gives a rich orange colored solution both in alcohol and water; 
and forms insoluble salts of much interest, with many metallic 
chlorids. Those with the alkaline metals are the most im- 
portant. The double chlorid of platinum and potassium is 
a very sparingly soluble salt, (PlCl a KCl,) which falls as a 
yellow, highly-crystalline precipitate, when chlorid of plati- 
num is added to a solution of chlorid of potassium. The 
double chlorid of sodium and platinum (PlClgNaCl+GHO) 
is, on the other hand, very soluble, and forms large beautiful 
yellowish-red crystals in a dense solution. Potash and 
soda are most easily separated, by the different solubility of 
their double platino-chlorids. The double chlorid of am- 
monium and platinum (PlCl a NH 4 Cl) is the orange precipi- 
tate before named, and is the best test to determine the 
presence of platinum in a solution. 

Associated with platinum are iridium, osmium, rhodium, 
and ruthenium — metals whose rarity permits us to pass them 
with a very brief mention. 

636. Iridium (Eq. 99) is found alloyed with osmium, 
forming the mineral iridosmine, IrOs„ in flat scales, mal- 
leable with difficulty. It is the hardest alloy known, 
being as hard as quartz. It is very infusible. It is true tin- 
white, crystallizes in hexagonal forms, and its density is from 
19*3 to 2112 being the densest body known. This mineral 
is much used to point gold pens. It is unacted on by aqua 
regia. It forms four oxyds. 

Osmium (Eq. 99*6) has a density of 10, of a bluish-white 
color, is neither fusible nor volatile, and forms, by its com- 
bustion in air, the very volatile and poisonous osmic acid 
0s 4 . It forms five oxyds, OsO, Os,0 8 , Os,0, Os 8 0, and Os 4 0. 
Fused with nitre, osmium forms osmiate of potassa. 

Describe the double chlorids of platinum and the alkalies, their prepa- 
tion and characteristics. What metals are associated with platinum f 
636. What of iridium ? What use has iridosmine ? What is the density 
of iridium? What of osmium? Its oxyds? 




Rhodium (Eq. 52*2) is so named from the rose color of its 
salts. It is a reddish-white metal, density about 10*5, and 
resembles iridium in hardness, fusibility, and malleability, 
as well as in resisting the action of acids. It forms two 
oxyds, RhO and Rh a 8 . 

Ruthenium (Eq. 52*2) is another metal obserred lately, 
to the extent of 5 or 6 per cent., in the iridosmine. Its den* 
sity is ahout 8*6. It is very like iridium in all its charac- 
ters, and has until lately been confounded with it 

What of rhodium? Its color and density? Its oxyds? What ©I 
nthenu* m ? Where found ? What relations has it ? 





[Thi last edition of this work was written about five years since, and 
having been desired to prepare this portion of the book for a new edition, 
it was thought proper to re-write it almost entirely. The views of chemical 
theory here adopted, have been in part advanced in the pages of the "Ame- 
rican Journal of Science" during the last four years. I have there at- 
tempted to point out what I conceive to be true in the respective systems 
of Giessen and Montpellier; and have laid down certain principles, which, 
in the present work, have been applied to the elucidation of a variety 
of questions. I have refrained from here developing at full length my 
own theoretical views, as being from their novelty unsuited to the cha- 
racter of an elementary treatise. 

It has been my plan to select from the great amount of matter which 
the chemistry of the carbon series now embraces, those subjects whose his- 
tory is well known and best fitted to illustrate the theory of the science, 
and at the same time to include the matters most interesting, in a practical 
view, to the medical and general student Both these classes will, how- 
ever, find it necessary to resort to more extended works for the history 
of many series of compounds, which have been omitted or very briefly 
noticed in these pages; while, on the other hand, it is hoped that the more 
advanced student will not find tho work unworthy of a perusal. 

I have not thought it necessary in an elementary treatise to cite 
authorities; but I may remark that I have availed myself of the works 
of Liebig, Gerhardt, and Gregory, and of the various chemical memoirs 
which have appeared in the different scientific periodicals for the last few 
yean. The most recent discoveries in organic chemistry are here em- 


Mohtkbal, Canada East, July, 1852.] 

Nature of Organic Bodies. 

637. Definition. — The name of Organic Chemistry is used 
to designate that branch of the science which investigates the 
phenomena and results of organic life, examines the che- 
mical relations of animals and plants, and the properties and 




transformations of the peculiar bodies which they afford. 
The constituents of organic bodies are comparatively few in 
number. Carbon with oxygen, hydrogen, and nitrogen, 
form all the combinations peculiar to organic substances. 
In addition to these, however, sulphur, phosphorus, and 
iron sometimes occur in small quantities in organio products; 
and the results of their decompositions and transforma- 
tions under the influence of different reagents, give rise to 
an immense number of compounds, in which, with the four 
organic elements already mentioned, are often united sul- 
phur, phosphorus, arsenic, antimony, chlorine, bromine, 
iodine, and the metals. 

638. It was formerly supposed that the production of the 
so-called organic substances was exclusively the prerogative 
of life. But later discoveries have shown that it is possible 
so to combine the organic elements as to form many of the 
products which were formerly obtained only through the 
medium of plants and animals. Hence the distinction be- 
tween organic and inorganic chemistry is no longer so well 
defined as before. But as in organic bodies carbon is always 
present, and is the only constant element, we may define or- 
ganic chemistry as the chemistry of the compounds of carbon. 
We may distinguish in mineral chemistry many such classes 
of compounds; as the nitrogen series, in which nitrogen is a 
constant and characteristic element; the silicon series, in- 
cluding all the silicious compounds: so in studying the 
chemistry of organic bodies, we find that they may all be re- 
duced to one, tlie carbon series. 

639. Among the organic matters which make up the 
structure of living beings, we must distinguish two classes : 
first, organized substances, which show either to the naked 
eye, or under the microscope, a peculiar structure, entirely 
different from that of crystallization, and never exhibited 
except in those matters which have been formed under the 
influence of the vital force : such are the woody and muscular 
fibres, the cellular and vascular tissues, the globules of 
blood and of starch (which see). These are not always 
homogeneous chemical compounds, and art, even could it 
imitate their chemical constitution, will never succeed in 
giving them their organized forms. The power which effects 
this must ever remain one of the secrets of life. 

The second class of organic substances includes those 
which are either produced by the destruction of organized 




bodies, or are the secretions or excretions of organized 
beings. They are subject to the same laws of form as in- 
organic bodies, and are liquid, solid, or gaseous, crystallized 
or amorphous. It is this second class of organic substances 
which we are able to form artificially, and which are pro- 
perly in the domain of the chemist ; among these are in- 
cluded the various alcohols, oils, acids, resins, sugars, gums, 
alkaloids, and coloring matters. 

640. The immediate effect of chemical agencies upon or- 
ganized bodies is to produce disorganization, and to convert 
them into substances which belong to the second class. 
Hence the study of organized structures belongs to the phy- 
siologist, and it is only where he leaves them that the 
chemist begins. The effect of strong heat upon organic 
bodies is peculiar. They are completely decomposed into 
a variety of products, among which are water, carbonic acid 
gas, carburets of hydrogen, and, if nitrogen be present, am- 
monia. The carbon, which is generally present in larger 
quantity than is required to form- these compounds, remains 
in the form of charcoal; hence organic bodies are always 
more or less combustible, and, unless volatile,. generally char 
or blacken by heat. 

641. In addition to the bodies of the carbon series, both 
animals and vegetables contain salts of potash, soda, lime, 
magnesia, and iron, with sulphuric, phosphoric, and silicic 
acids, chlorine and fluorine. Animals also secrete phosphate 
and carbonate of lime to form their bones, as in vertebrates, 

' and their external coverings, as in the mollusca. These salts 
have been already described under their proper heads, in 
the Inorganic Chemistry, and their relations to life will be 
considered in the section on the nutrition of animals and 

Laws of Chemical Transformations. 

642. The various changes met with in the study of or- 
ganic substances, resulting in the destruction of existing 
combinations, and the formation of new ones, may conve- 
niently be reduced to two classes ; first, equivalent substitu- 
tions, and second, direct union. It will oe shown that, in 
the first case, decomposition and recomposition are reciprocal 
and simultaneous, so that the one implies the other, and we 
investigate at once the laws of both. In the second case, 
this relation apparently does not exist ; but there is a direct 




decomposition which is the converse of direct union, and 
consists in the partition or dissection of a compound into 
two or more compounds having a lower equivalent. 

Equivalent Substitution. 

648. The law of substitution is, that one or more atoms 
of an element in a compound may be replaced by any other 
element, or group of elements, which are equivalent in their 
chemical relations; and the chemical constitution of the 
compound remain unchanged. Thus acetic acid C 4 H 4 4 
may lose three atoms of hydrogen and take in their place 
three equivalents of chlorine, which last are substituted for 
the hydrogen, without changing the acid constitution of the 
body j the new compound, chlorqcetic acid, C/HC1 3 )0 4 
closely resembles acetic acid in its properties. Here 35*5 
parts of chlorine are equivalent to 1 of hydrogen, and Cl 3 is 
equivalent to H 3 , and may be substituted for it without 
altering the type of the compound. Bromine and iodine, 
and perhaps fluorine, may replace hydrogen in a similar 

644. In the foregoing reaction C 4 H 4 4 and Cl fl are con- 
cerned, and C^HCl^O, and 3(C1H) are the results. We 
shall show farther on, from a consideration of their combining 
volumes, that as the equivalent volume of chlorohydric acid 
is (HC1), that of hydrogen is (HH), and that of chlorine 
(C1C1). In the reaction between acetic acid and chlorine, 
there are then but three equivalents or volumes of chlo- 
rine, 3(C1C1), and each successive volume exchanges one* 
of its atoms for one of hydrogen: thus, (C 4 H 4 4 )-f-(ClCl) 
=(C 4 H 3 C10 4 )+(CIH)— and so on with a second and third 
volume of chlorine. In many instances we can trace the 
successive steps by which atom after atom of hydrogen is 
replaced by chlorine, a corresponding equivalent of hydro- 
chloric acid being simultaneously formed. The law of equi- 
valent substitution is then reducible to that which has 
been called double elective affinity, and always supposes the 
reaction of two complex bodies, which give rise to two new 

645. As hydrogen is replaceable by CI, Br, and I, so 
oxygen is caf>able of being replaced by sulphur, selenium, 
and tellurium. This can seldom be effected directly, as in 
the case of chlorine and hydrogen, but it is obtained by in- 
direct decompositions. Alcohol, which is Gfifi^ gives suU 

Digitized by VjOOQ iC 


pkur alcohol, C 4 H 8 S 3 , and the selenium compound will bo 
C 4 H 6 Se 3 . Mineral chemistry affords similar instances; 
sulphate of soda is 2SOg-f-2NaO, or S 3 Na 3 8 , while the hypo- 
sulphite of soda is SjjNa 3 (0 3 S 6 ), and another salt is S^a, 
(0 4 S 4 ). These different sulphates crystallize with the same 
amount of water, have the same form, and the same solu- 

Nitrogen, phosphorus, arsenic, and antimony, which form 
a natural group, may also replace each other, equivalent for 
equivalent ; thus, glycocoll, which is C 4 H 5 N0 4 , has a corre- 
sponding arsenical conipouud, alkargene, C 4 H 5 As0 4 . 

646. When any acid, like chlorohydric or acetic acid, acta 
upon a metal such as zinc, hydrogen is evolved, and a chlo- 
rid or acetate of zinc is formed, in which Zn has replaced 
the hydrogen, HCl+Zn=H+ZnCl, and C 4 H 4 4 -f-Zn= 
C 4 H 8 Zn0 4 -f-H. If chlorine (C1C1) acts upon zinc, we ob- 
tain the same chlorid as with chlorohydric acid, (ClCl)-f-Zn f 
=2(ZnCl), and when chlorine combines with hydrogen, it is 
(ClCl)+(HH)=2(HCi). Now as the action of HC1 upon zinc 
evolves hydrogen (HH), all these analogies lead us to conclude 
that the equivalent of zinc is Zn 3 =(ZnZn), and hence that 
in the case of acetic or chlorohydric acids, an equivalent of 
zinc reacts with two equivalents of the acid. Acetic acid 
C 4 H 4 4 +ZnZn=C 4 (H 3 Zn)0 4 +(ZnH), but ZnH with an- 
other equivalent of C 4 H 4 4 yields a second equivalent of 
acetate and one of hydrogen (HH). The hydrates of metals 
like ZnH are seldom stable, and as they decompose water 
,and acids very readily, are difficult to be isolated. The re- 
placement of the hydrogen in acids by a metal is then ana- 
logous to that of its substitution by chlorine. 

647. When an acid is brought in contact with a metallic 
oxyd, double decomposition ensues in the same manner, 
but with the formation of an oxyd of hydrogen ; acetic acid 
C 4 H 4 4 +ZnO=C 4 H 8 Zn0 4 -f HO. But with the equiva- 
lents here proposed, the composition of oxyd of zinc must 
be written Zn 3 2 , and that of water H 3 3 , so that as in 
the reaction with metallic zinc, two equivalents of the 
acetic acid react with Zn 3 3 . If we represent the actions 
as consecutive, the first result will be (ZnH)0 3 , or the 
hydrated oxyd of zinc, corresponding to ZuH, which with 
another equivalent of acid exchanges its Zn for H, forming 
water, (H a 3 ). 

648. All the metals proper are capable of replacing in this 




manner a portion of the hydrogen of acids to form salts. 
A great number, like acetic acid, have only one atom of 
hydrogen which can be replaced by a metal, bnt in others 
two and three atoms may be in a similar manner replaced. 
These are called bibasic and tribasic acids; while such as 
acetic acid are said to be monobasic. Tartaric acid is bibasic; 
its composition is represented C 8 H 9 18 , or C 8 H 4 (H 8 )0 18 j 
the two equivalents of hydrogen may be replaced by two 
equivalents of some metal as C s H 4 Zn 9 ia ; by two dif- 
ferent metals as in C s H 4 (KNa)0 18 , or but one equivalent 
may be replaced as in C 8 H 4 (HK)0 18 . The latter still 
retains acid properties, and is called an acid salt The salts 
of tribasic acids may contain either one, two, or three equiva- 
lents of hydrogen replaced by a metal; the first two of 
these salts will be acid, and the last neutral. 

The monobasic acids are almost always volatile, while 
the bibasic and tribasic acids are never volatile without 

649. The sesquioxyds, which have been represented in 
treating of mineral chemistry as composed of two equivalents 
of a metal combined with three of oxygen, offer a peculiar 
case in the formation of salts. If we take, for example, the 
peroxyd of iron, Fe s 8 , we find that it saturates, not twe 
equivalents of acetic acid, but three, and that while in the 
acetate of the protoxyd of iron FeO replaces H, in the acetate 
of the peroxyd two- thirds of an equivalent of iron sustain the 
same relation ; if then we would represent the acetate of the 
peroxyd, we must write it C 4 H 8 Fe|0 4 . In other words 
Fe fl O a has reacted as if it were 3(FeJO). But if we ex- 
amine these two salts still farther, we find that in their che- 
mical reactions they differ from each other as widely as the 
salts of two distinct metals, and that we have in the salts of 
the peroxyd, iron with two-thirds its ordinary equivalent, and 
with peculiar and distinct properties. We may designate 
the iron in the proto-salts hs/errosum, with an atomic weight 
of 28 and the symbol Fe, and the iron in the persalts as 
ferricum, with an atomic weight of 18*6, and write its 
symbol, fe. The sesquioxyd of iron, Fe a 8 , is then 3(feO) 
and the corresponding acetate of ferricum 4 H 8 feO 4 . 

This same view is to be extended to the proto and ses 
qui-salts of chromium and manganese, and to the salts of 
alumina, which is a sesquioxyd ; also to the salts of mercury 
and of tin, in which the equivalents of the two forms are to 




each other as 1 : 2. We have ckromosum and chromicum, 
aluminicum, stannosum and stannicum, mercurosum and 
mercuricum; the second form of the metal is distinguished 
hy writing its symbol with a smaty letter as Cr, cr, al, Sn, 
«*; Hg, hg, &c. 

650. We have seen that acetic aojd may exchange three 
equivalents of hydrogen for chlorine, and but one equiva- 
lent for a metal, so that in chloracetate of silver, C 4 C1, Ag0 4 , 
all the hydrogen is replaced. There are many acids in 
which we cannot effect the substitution by chlorine, nor can 
the fourth atom of hydrogen in acetic aoid be thus replaced; 
it can be removed only by substituting a metal. Thus the 
hydrogen which is replaceable by chlorine is distinct from 
that which is equivalent to a metal. It will be shown far- 
ther on, however, that there are some bodies in which this 
distinction appears to be lost, and in which all the hydrogen 
may be replaced either by chlorine or a metal. 

651. In treating of the action of chlorine upon acetic 
acid, we have considered the process only with reference to 
the acid ; but the substitution is reciprocal, and there is 
mutual decomposition. To make the question more simple, 
we will select a case where but one atom of hydrogen is 
replaced. The essence of bitter almonds, benzoilol, has the 
composition C^HgOj, ; by the action of chlorine, hydrochlo- 
ric acid is formed, and one atom of hydrogen is replaced by 
chlorine, C 14 H 6 fl +(ClCl)=C 14 H 5 C10 fl +H CI. Now if we 
consider only the oil, it will be said that an equivalent 
substitution has taken place of CI for H ; but it is equally 
correct to say, that the benzoilol minus H has replaced CI in 
the equivalent of chlorine (C1C1) ; in other words, that the 
essence has ceded H to form hydrochloric with CI, and that 
the residue has replaced the eliminated atom of chlorine. 

When the constitution of the bodies becomes more com- 
plex, the action is still the same ; benzoilol reacts with nitric 
acid, which is NH0 8 , and yields water and a new substance 
containing the elements of the essence and the acid, minus an 
equivalent of water; C 14 H 6 O fl +NHO =C 14 H 5 NO fl +H a O 9 . 
An examination of this reaction leads to the conclusion 
that the acid has furnished H and the essence HO a to 
form the equivalent of water ; so that the residues C 14 H fc 
and N0 6 unite to form the new product; and it may be 
said that C 14 H 5 replaces H in the nitric acid, precisely as 
C 14 H 4 a replaces CI in the equivalent of chlorine. 




652. The monobasic nitric acid has fixed the element* 
of a neutral body in place of its atom of hydrogen, and 
the nitrobenzoilol is hence neutral. But if benzoic acid, 
which is monobasic, be substituted for the essence, it pre- 
serves even in combination its saline character; and hence the 
compound has the monobasic character which pertains to the 
benzoic acid. And even if this nitrobenzoic compound re- 
places the hydrogen of a second atom of nitric acid, the mono- 
basic character is still preserved in the resulting compound. 
A bibasic acid, like the sulphuric, will form with one equiva- 
lent of a neutral substance a monobasic acid; and with two, 
a body which shall itself be neutral ; because in these cases, 
one and two atoms of hydrogen have been removed from the 
acid. But if an equivalent of a monobasic acid reacts with 
sulphuric acid, it still retains its saline power in combina- 
tion, and the result is bibasic : in like manner, with another 
bibasic acid, sulphuric acid yields a compound which is triba- 
sic. In all these reactions, as io the formation of nitroben- 
zoilol, corresponding equivalents of H 9 9 are eliminated, and 
the derived bodies are often designated as coupled acids. 

653. Some writers have distinguished these cases from the 
simpler instances of equivalent substitution, and have desig- 
nated them as substitutions by residues. But this distinction 
originates in a too much restricted idea of the meaning of 
an equivalent. In an early period of the science, the 
equivalent of a metal was fixed from the proportion of hydro- 
gen it replaces, or in other words from the composition of 
its salts; but we have since learned that although 28 parts 
of manganese are generally equivalent to 1 of hydrogen and 
35-5 of chlorine, there are cases where, as in permanganic 
acid, which corresponds to perchloric acid, 56 parts of 
manganese are equivalent to 35*5 of chlorine; and in the 
sesqui-salts of the metal, 18 6 of manganese become equiva- 
lent to H; so 31-7 parts of copper are at one time equiva- 
lent to one of hydrogen, and 63*4 parts at another time. 
Hence the numbers assigned as the equivalents of the 
elements are changeable as these elements change theif 
functions, and, as in the case of benzoilol, groups of carbon 
and hydrogen, or carbon, hydrogen, and oxygen, may become 
equivalent to a single atom of chlorine of hydrogen or a 
metal, and may replace it in combination. 

These groups which replace the metals on the one hand, 
and chlorine and bromine on the other, have been described 




by some authors by the name of compound radicals, and 
have served as the basis of a system of organie chemistry 
and of nomenclature. But as we conceive that the system 
is liable to great objections, and tends to perpetuate false 
notions of the science, the language of the compound radi- 
cal theory will not be employed in these pages. 

654. The law of direct union is much more simple. A 
salt may assimilate the elements of water, or of a metallic 
oxyd, or ammonia may combine with an acid, as with hydro- 
chloric acid, to form sal-ammoniac; NH 8 - r -H01=NH 4 Cl. 
A carbon compound, like olefiant gas, C^H^ may also 
unite directly with Cl 3 , to form C 4 H 4 C1 8 . In these and 
similar instances there is only one product, a character by 
which such reactions are distinguished from those of the 
first class. On the other hand, a body may eliminate the 
elements of water or of hydrogen, or some similar sub- 
stance, and thus resolve itself into two ; for instance, alcohol 
C 4 H fl fl , under the influence of certain reagents, may lose 
H 8 , and in some of its combinations is resolved by heat 
into C 4 H 4 , and H fl 9 . Many ammoniacal salts which are 
formed by direct union of the acid and ammonia, separate 
under the influence of heat into water, and new compounds 
called amids, which, when placed in contact with water, 
under proper conditions, combine with that substance, and 
regenerate the original salts. 

655. The compounds formed by direct union may then 
divide in a manner different from that of their composition, 
and thus produce two new compounds unlike the parent 
ones, precisely as in the reactions of the first class. We 
hence arrive at the conclusion, that the phenomena of the 
second class represent only an intermediate step in the pro- 
cess of equivalent substitution ; and that if we could arrest 
the latter process, we should always find it to consist of two 
parts, composition and decomposition, resulting in a mutual 
substitution. As an illustration, may be cited the com- 
pound formed by the direct combination of chlorine with 
olefiant gas, which is C 4 H 4 Cla, but under certain circum- 
stances is decomposed into HC1 and C 4 H S C1 ; the latter is a 
substitution product from olefiant gas, and we are here enabled 
to see the intermediate step in its formation. 

The two classes into which we have for convenience di- 
vided the phenomena of chemical transformations, are then 
reducible to one simple formula; a+6 and c-\-d may unite 





to form a-\-b-\-c-\-d y and may afterward be rearranged so as 
to form a-\-c and o-f-e?, as in the first, or a-\~b and c-f-d, as in 
the second case. 

On Combinations by Volumes. 

656. The law of combination by volumes has already 
been given in the first portion of this work (257) ; but we 
refer to it again to explain the density of vapours, and the 
equivalents of organic substances. 

The proportions in which oxygen and hydrogen unite to 
form water are one volume of the former to two volumes 
of the latter, and these three are condensed into two volumes 
of the vapor of water at 212° F. As these proportions have 
been assumed to correspond to one equivalent of each, the 
composition of water is written HO, having an equivalent 
number of 1+8=9, and corresponding to two volumes of 

The specific gravity of hydrogen has been found by experi- 
ment to be 69-2, air being 1000, while oxygen is 1105*6. 

2 volumes of hydrogen 2 X 60*2.. 138*4 

1 M of oxygen 1105-6 

yield 2 volumes of vapor water. 1244*0 

1 " of do. do 6220 

Experiment gives for the density of water vapor 620*1. 

657- Density of Carbon Vapor. — In calculating the atomic 
volume of bodies of the carbon series, it becomes necessary 
to fix upon the density of carbon vapor; but as carbon is 
not known in a gaseous form, we must deduce its density 
from that of some one of its compounds. 

When carbon is burned in oxygen gas, this is converted 
into carbonic acid gas without change of volume. If we 
subtract from the weight of the new compound that of the 
oxygen, we shall then have the weight corresponding to the 
caibon vapor. Experiment has given for the density of 

Carbonio acid gas (air = 1000) 1529*0 

Deduct that of oxygen 1105*6 

Gives for the density of carbon vapor 423*4 

If we suppose the gas to consist of two volumes of carbon 
vapor and two of oxygen condensed one-half, the equivalent 
volume of carbon will be the same as that of hydrogen, and 
its weight represented by the above number. But if it 
may, with as good reason, be regarded as formed by the con 

Digitized by VjOOQ IC 


densation of two volumes of oxygen and one of carbon vapor 
into two volumes, the density of carbon vapor will be twice 
the number calculated, or 846 8. 

The experimental density of carbonic acid is, however, 
not very exact, and the density of carbon vapor may be 
more accurately calculated from the well-determined density 
of oxygen. Carbonic acid consists of oxygen 72*73 and 
carbon 27*27 parts, and the observed density of oxygen is 
1105*6; we have then this proportion: 

72-73 : 27-27 : : 1105-6 :x. 
in which x = 829, which we shall adopt as the most correct 
number for the density of carbon vapor. 

658. Hence, if we know the composition and equivalent 
of any body, we can calculate its density ; or, having the 
density and composition given, can fix its equivalent. For 
example, the density of defiant gas, as found by experiment, 
is 9674. It consists of equal equivalents of carbon and hy- 
drogen, and one volume of it contains 

2 volumes of hydrogen = 1 eq. 2x69-2 138-4 

1 " of carbon vapor = 1 eq . 829-0 

Yield 1 volume of olefiant gas 967*4 

If now the equivalent of olefiant gas be like that of water 
represented by two volumes, the formula will be C a H 3 ; but 
most writers have assumed four volumes as representing the 
equivalent of organic compounds; while water is written HO, 
and corresponds to but two volumes of vapor. Thus the 
the formula of olefiant gas is generally written C 4 H 4 = four 
volumes of vapor ; to be compared with this, water must be 
H fl O fl . Some of the French chemists, choosing to preserve 
the old equivalents of organic bodies, have doubled in this 
manner that of water; while others have preferred to divide 
the formulas of organic substances, and reduce all to the 
standard of two volumes, oxygen being one; or, in other 
words, to take the volume of the atom of hydrogen as unity. 
We shall in these pages regard H a , which is equivalent to 
four volumes, (0 being one volume,) as unity, and write the 
formula of water H a O a , with an equivalent of 18. 

On the Law of the Divisibility of Formulas. 

659. The researches of Gerhardt and Laurent have esta- 
blished a very important law which prevails in the grouping of 
elements in compounds, not only in those of the carbon series. 




bat also in mineral chemistry. It is, that in all compounds 
of carbon, hydrogen, and oxygen, represented by an equiva- 
lent of four volumes of vapor, the number of atoms of carbon 
and oxygen is always divisible by two, and that of the atoms 
of hydrogen by the same number. If the oxygen is wholly 
or in part replaced by sulphur or selenium, the substitution 
is always atom for atom, so that the same divisibility is 
maintained; and if the hydrogen is replaced in whole or in 
part by chlorine, iodine, or bromine, by nitrogen, phospho- 
rus, arsenic, or antimony, or by any of the metals, the sum 
of the number of the atoms will always be a multiple of two* 

On Isomerism. 

660. We have seen, in treating of substitution, that a num- 
ber of the atoms of any element in a compound may be re* 
placed by another element, and the constitution of the body 
remain unchanged. From this, and from other facts, we con* 
elude that the properties of compounds depend rather upon the 
peculiar arrangement, than upon the species of their consti- 
tuent atoms; and, moreover, that a different arrangement of 
the same elements may form compounds very different in 
their properties. Such bodies are frequently met with among 
the carbon series, and are denominated isomeric compounds, 
(from isos, equal, and meros, measure.) We have an instance 
in the essence of spiraea ulmaria, and benzoic acid, both of 
which are represented by the formula C^HgC^, but are very 
distinct in their characters. The relation of such as have 
not only the same proportional, but the same actual com* 
position, may be distinguished by the term metamerism, 
(from meta f by, and meros, measure.) 

Another form of isomerism is that in which the relative 
proportions of the elements being the same, the equivalent 
of the one is a multiple of the other. Thus, defiant gas 
C 4 H 4 , butyrene C S H 8 , naphtene C 16 H l6 , and cetene C^B.^ 
have the same proportions of carbon and hydrogen, though 
each has a density and equivalent double that of the pre- 
ceding; such bodies are said to be polymeric, (from polus, 
many, and meros.) 

The phenomena which in mineral chemistry have been 
characterized under the names of dimorphism and aUotiro* 
pism are instances of isomerism which is often polymeric, and 
are met with even among bodies which are considered as 




On Chemical Bbmologues. 

661. The carbo-hydrogens just mentioned, whose com- 
position is represented by a multiple of C 4 H 4 , are possessed 
of similar chemical affinities, and form with other substances 
similar compounds. Two of them, the first and last, are arti- 
ficially formed from compounds which have the formula 
C 4 H 6 a and C^H^O,,, and differ from their respective hydro- 
oarbons only by the elements of water. 

These compounds are two terms of a series of bodies which 
are known as alcoJwls, from common alcohol, which was the 
first known of the series. The first one has the formula 
C a H 4 a =C a H a -fH a a , and the next C 4 H 6 O a , each one dif- 
fering from the last by C a H a ; so that representing by n any 
number divisible by two, the general formula of the series 
will be C m H n +H a O a , or C^H^C^. Bodies thus related 
are designated komohgues; and the study of this relation- 
ship, which was first pointed out by Gerhardt, is of the high- 
est importance to the science. 

The bodies of an homologous series generally undergo simi- 
lar changes by like reagents, and the products resulting are 
also homologous. Thus, wine alcohol , by oxydizing agencies, 
loses Hj, and forms the body C 4 H 4 a ; by further oxydation 
it yields acetic acid C 4 H 4 4 ; and every alcohol in like man- 
ner yields an acid homologous with the acetic acid : the ge- 
neral formula of the series being C ll H n 4 . The intermediate 
body C^B^Oj, has not, however, in all cases been obtained. 

The alcohols also yield a series of homologous alkaloids, 
whose common formula is (C^H^HgN or C.H^gN. 

662. In many homologous series the number of equiva- 
lents of hydrogen is not equal to that of the carbon, and 
the formula must be written differently. Thus, benzoic acid 
C 14 H 6 4 and cuminic acid C ao H ia 4 are homologous, and 
diner from each other by (C a H a ) 3 , and we may express 
them by the general formula C„H 1l _ 8 4 , the number of equi- 
valents of hydrogen being less by eight than that of carbon : 
by this it will be seen that the lowest term of the series will 
be that in which n — 8 =2, or C 10 H a 4 ; for if n — 8 =zero, 
the compound will contain no hydrogen, and hence want the 
^characteristic properties of an acid which belong to the series, 
*If, however, the hydrogen be present in excess, the case will 
be different. In the formula of the alcohols, if n = zero, the 
representative of the type, is H^O^ or water, which is the 




prototype of the alcohol series ; and in the alkaloids of th<s 
same group, when n=zero f we have NH S , or ammonia, which 
is equally their prototype. 

It will be seen from what we have said of isomeric bodies 
that there may be two or more series of homologous bodies, 
which shall be metameric of one another, and hence simi- 
larity of chemical characteristics is necessary to constitute a 
homology. In an homologous series of chemically allied 
compounds, then, while the oxygen and nitrogen always 
remain the same, the proportions of hydrogen and carbon 
vary by a simple and constant ratio. 

Temperature of Ebullition. 

663. A simple relation between the boiling points of 
different members of an homologous series has been pointed 
out, which may often serve an important end in deciding the 
equivalent of a compound. The boiling point of the volatile 
acids of the formula CJEI.C^ is found to increase about 
86° F. for each addition of C a H a . 


664. The ultimate analysis of organic substances is of 
great importance : for as we are unable to form them by a 
direct combination of their elements, a correct understanding 
of their composition, and of the nature of the changes which 
they undergo, must depend entirely on the results of their 
analysis. The equivalent of many substances is so large, 
that a change of one-hundredth part in the proportions, gives 
to the compound entirely distinct properties. Great refine- 
ment is consequently necessary in analysis, to enable us to 
detect the minute differences in composition ; and such have 
been the care and skill with which the subject has been 
studied, that we have now arrived at very great accuracy 
in operations of this kind. 

665. In theory, the process of organic analysis is ex- 
ceedingly simple. If any organic substance, as sugar, for 
example, is heated with a body capable of yielding oxygen, 
such as the oxyd of copper, of lead, or any other easily re- 
ducible metal, it is completely decomposed ; the carbon and 
hydrogen take oxygen from the metallic oxyd, and are wholly 
converted into carbonic acid and water. From the weight 
of these, it is easy to calculate the amount of carbon and 
hydrogen in tne body, and if it contains no other element 

Digitized by VjOOQ IC 


except oxygen, this is known by the loss. But notwith- 
standing the theoretical simplicity of the process, its accurate 
execution is exceedingly difficult, and very many precautions 
are necessary to insure accuracy. It is not the object of this 
work to explain all the precautions necessary to the successful 
performance of analytical operations, but merely to give an 
outline of the method pursued, and a general idea of the means 
employed. For more particular information, the student is 
referred to an excellent memoir on this subject, by Liebig. 
666. The operation is performed in a combustion tube of 
hard glass, from 12 to 18 inches in length, and from T 4 to T 5 9 
of an inch in diameter. One end is drawn out to a point, 
turned aside and sealed. Oxyd of copper, prepared from 
the nitrate, is generally employed for the combustion. 
Just before using it, it is heated to redness, in order to expel 
the moisture which it readily attracts from the atmosphere ; 
the combustion tube is then about two-thirds filled with the 
hot oxyd. The substance to be analyzed having been care- 


'Oxyd. Mixture. Oxyd. 

Fig. 394. 
fully dried, five or six grains of it are weighed out in a tube 
with a narrow mouth, in order to prevent the absorption of 
moisture. It is then rapidly mixed in a warm and dry por- 
celain mortar, with the greater portion of the oxyd from the 
tube, to which it is again transferred, and the tube is then 
nearly filled up with pure oxyd. The relative portions of 
the oxyd and mixture are shown in fig. 394. 

667. However carefully the mixture has been made, a 
little moisture will have been absorbed from the air, which 
must be removed by the following arrangement : — To the 
end of the combustion tube is fitted, by means of a cork, a 
long tube filled with chlorid of calcium, and to this is at- 
tached a small air-pump, fig. 395. The combustion tube is 
covered with hot sand, and the air slowly exhausted. After 
a short time, the stopcock is opened, and the air allowed to 
enter, thoroughly dried by its passage over the chlorid of 
calcium. It is again exhausted, and this process repeated 
four or five times, by which the mixture is completely dried. 





Fig. 395. 
668. The tube is now ready for the combustion, and is 

placed in the 
furnace, figure 
396. This is 
constructed of 
sheet iron, and 
*»g.3fle. fitted with a 

series of supporters at short distances from each other, to 
prevent the tube from bending when softened by heat. The 
furnace is placed on a flat stone, or tile, with the front 
slightly inclined downward. The quantity of water form- 
ed in the process is estimated by a light tube, fig. 397, 

which is filled with frag- 

SfTPfhwiiif ffi^==a meDts of chlorid of calcium, 
Fig. 397. aQ d> *£ter having been very 

carefully weighed, is attach- 
ed by a well-dried and closely fitting cork, to the end of 
the combustion tube. To determine the carbonic acid, a 
small five-bulbed tube of peculiar form is used, called Liebig's 
potash bulb tube, fig. 398. It is charged for 
this purpose with a solution of caustic potash of 
a specific gravity about 1*25, with which the 
three lower bulbs are nearly filled. Its weight 
is determined with great exactness, and it is 
then attached to the chlorid of calcium tube, 
by a little tube of gum elastic, which is held 
fast by a silken cord. The whole arrange- 
ment is shown in fig. 399. The tightness of 
Fig. 398. the junction is ascertained by drawing a few 




Fig. 399. 

bubbles of air through the end of the potash tube, so that the 
liquid will be raised a few inches above the level on the 
other side ; if this level remains the same for some minutes, 
the whole apparatus is tight. 

669. Heat is now applied by means of ignited charcoal 
placed around the anterior portion of the tube, and when 
this is red-hot, the fire is gradually extended along the tube, 
by means of a movable screen, represented in the figure. 
This must be done so slowly as to keep a moderate and uni- 
form flow of gas through the potash solution. When the 
whole tube is ignited, and gas no longer escapes, the closed 
end of the combustion tube is broken off, and a little air 
drawn through the apparatus to remove all the remaining 
products of combustion. The tubes are then detached, and 
from the increase of weight in the chlorid of calcium tube, 
the amount of water, and thence that of hydrogen, is deduced. 
The carbon is determined from the increase in weight of the 
potash bulb tube, by a simple calculation. 

670. Volatile liquids are analyzed by enclosing them 
in a narrow-necked bulb of thin glass. The weight of the 
empty tube is first ascertained ; the liquid is introduced, 
the neck sealed, the weight being again ascertained, and 
the difference gives the weight of the 
substance. The neck of the bulb is 
then broken by a file mark at a, ('fig. 
400,) dropped into the closed end of 
the combustion tube, and covered with 
oxyd of copper, which should nearly fill 
the tube. When this is heated to red- 
ness, a gentle heat applied to the por- ( < 
tion of the combustion tube containing ii 
the volatile fluid, sends it in vapor over 
the ignited oxyd, completely burning it. Flg# 400# 
The products of its combustion are estimated as before. 




671. Fatty bodies, and others which contain much carbon 
and a small quantity of hydrogen, arc more perfectly burned 
by employing chromate of lead instead of copper. This sub- 
stance does not readily attract moisture from the atmosphere, 
like oxyd of copper, and is consequently better when the hy- 
drogen is to be determined accurately. The chromate of lead 
is prepared for use by heating it until it begins to fuse, and 
when cool reducing it to powder. 

672. When nitrogen is a constituent of organic bodies, 
it is determined by placing in one end of the combustion 
tube about three inches of carbonate of copper, secured in 
its place by a plug of asbestus ; and then the nitrogenous 
body is introduced, mixed with oxyd of copper. The re- 
maining space in the combustion tube is filled with turnings 
of metallic copper. The air is then withdrawn by an air- 
pump, and a gentle heat applied to the carbonate of copper, 
which evolves carbonic acid, and drives out all remaining 
traces of common air. The tube is now heated as usual, 
and the gases evolved are collected in a graduated air-jar, 
over mercury. When the combustion is finished, heat is 
again applied to the carbonate of copper, and another portion 
of carbonic acid expelled, which drives out all the nitrogen 
from the tube. The use of the copper turnings is to decom- 
pose any traces of nitric oxyd which may be formed in the 
process. The carbonic acid is removed from the air-jar by 
a strong solution of potash, and pure nitrogen remains, 
which is measured with the usual precautions, and from its 
volume the weight is easily determined. 

673. Another and a preferable mode of determining nitro- 
gen, is that of Will and Varrentrapp, which is founded on the 
Fact that when a body containing nitrogen is heated with an 
excess of caustic potash, or soda, all the nitrogen is evolved 
in the form of ammonia, and may be thus estimated, by con- 
ducting it into hydrochloric acid, and forming, with chlorid 
of platinum, the double chlorid of platinum and ammonium. 

674. Chlorine is determined in the analysis of organic 
compounds, by passing the vapor over quicklime heated to 
redness in a combustion tube ; chlorid of calcium is formed, 
which is afterward dissolved in water, and the chlorine 
precipitated by nitrate of silver. From the weight of the 
chlorid of silver, the amount of chlorine is calculated. 

675. Sulphur is a rare constitutent of organic compounds. 
Its presence is detected by fusion with nitre and carbonate 





ef soda, or by digestion with nitric acid. Sulphuric acid is 
thus formed, and is precipitated as sulphate of baryta, from 
the weight of which that of the sulphur is determined. In 
the analysis with oxyd of copper, a small tube of peroxyd 
of lead is introduced between the chlorid of calcium tube 
wd the potash apparatus, to absorb the sulphurous acid 
which is evolved. 

Density of Vapors. 

676. The determination of the destiny of vapors is of 
great importance ; in the case of some volatile organic com- 
pounds which form no combinations with other substances, it 
is the only means of ascertaining their constitution and equi- 
valent. The process is very simple, and the method employed 
in the case of gases has been already described, (49.) When 
the substance is a liquid or solid, it is introduced into a narrow- 
necked glass globe, of the form represented in fig. 401, the 
weight of which is carefully ascertained. The 
globe is held by means of a handle firmly 
attached by a wire, beneath the surface of an 
oil or water-bath, and then heated to some 
degrees above the boiling-point of the sub- 
stance. When this is all volatilized and the 
globe is filled with the vapor, the open and 
projecting end of the globe's neck is sealed 
by the flame of a spirit-lamp : at the same 
time the temperature of the bath is noted. 
When the globe is cooled it is again weighed, 
and the end of the neck broken off beneath 
the surface of mercury, which rushes up and 
fills the empty vessel. The mercury is then 
carefully measured. The capacity of the 
vessel and its weight being thus ascertained, we can find 
the weight of a volume of vapor at the observed tempera- 
ture, and by an easy calculation can determine what would 
be its volume at the ordinary temperature, (88:) its weight 
compared with that of the same volume of air gives the 
specific gravity required. 

677. It is proposed, before commencing the study of those 
bodies of the carbon series which we have included under 
the head of Organic Chemistry, to consider briefly the prin- 
cipal products of the ultimate decomposition of this class 
of substances. These are water, ammonia, and carbonic 

Fig. 401. 




acid gas. The latter only strictly comes within our limits, 
and all of them have been described in the first part of this 
work ; but we shall bring them np again to illustrate certain 
laws of substitution, which will help to explain the history 
of tho more complex organic compounds. 

We shall then treat of starch and sugar, and some other 
bodies of high equivalents, whose history is comparatively 
simple, and proceed to the products of their decomposition 
by fermentation and other means, among which are different 
alcohols and acids. 


678. In the first part of this volume, water has been de- 
scribed as having the formula HO, and as composed of two 
volumes of hydrogen and one of oxygen, condensed into two 
volumes of vapor of water ; we have already given the rea- 
sons which lead us to adopt four volumes as its equivalent, 
and to write its formula H s 9 . 

We shall now speak of the products of substitution de- 
rived from water. If the oxygen be replaced by sulphur 
we have sulphuretted hydrogen: the selenium and tellu- 
rium compounds have a similar composition. One or both 
atoms of the hydrogen may be replaced by a metal. Hy- 
drate of potash KO.HO is water in which one equivalent 
of H is replaced by potassium : it is (KH)0 9 , and anhy* 
drous potash will be K fl O a . The hydrated oxyds result from 
the replacement of one equivalent of hydrogen by a metal, 
while in the anhydrous oxyds both are thus replaced. 
Water thus resembles a bibasic acid, and the hydrated 
oxyds may be compared to acid salts, while the anhydrous 
oxyds are like neutral salts. 

679. The so-called suboxyds are illustrations of the 
change of equivalent upon which we have insisted. The 
red oxyd of copper is Cu s O, or rather 0u 4 O s , but copper 
here unites in twice its ordinary equivalent weight, and in 
this form, which we may designate as cuprosum, with the 
symbol cu, is strictly equivalent to H and to Cu, so that tho 
red oxyd is cu a O fl . The peroxyds, like those of hydrogen 
or barium, may be either oxyds which have combined with 
an additional amount of oxygen, and thus increased their 
equivalent weight, being H 2 4 and Ba s O*, or tbey may be 
regarded as sustaining to the ordinary oxyds the same re- 
lation that the black oxyd of copper does to the red oxyd, 




being compounds in which barium and hydrogen nnite in 
one-half their ordinary equivalent : thus, (Ba$) a O fl , &c. The 
same views apply to the persulphuret of hydrogen and 
Other persulphurets. From the volumes of the correspond- 
ing bodies of the carbon series, the first view is probably the 
true one. 

680. We have shown that in the group H 3 , chlorine may 
replace H to form chlorohydric acid, and we may here refer 
to an example in which an atom of the hydrogen is replaced 
by a metal. It is a product of the action of hypo-phosphorous 
acid upon a salt of copper, and is a yellow powder contain- 
ing Cu g H, which corresponds to euH. Chlorohydric acid 
dissolves it with the evolution of hydrogen and the forma- 
tion of a chlorid of cuprosum, cuH+HCl=cuCl+HH, 
the hydrogen of both being evolved. 

It has already been remarked that there are examples of 
bodies in which all of the hydrogen may be replaced either 
by chlorine or by a metal, and water is such a body; hydrated 
hypochlorous acid CIO, HO is (C1H)0 S , or water in which 
CI replaces H : the second equivalent of hydrogen may be 
replaced by a metal to form a hypochlorite, as in CIO.KO, 
which is (C1K)0 3 . But this second equivalent may also be 
replaced by chlorine, and we have the so-called anhydrous 
hypochlorous acid, which is Cl s O fl , or water in which chlo- 
rine has been substituted for the whole of the hydrogen. 


681. Ammonia is composed of six volumes of hydrogen 
and two of nitrogen (0 being represented by one volume,) 
condensed to one-half, or to four volumes : its formula is 
then NH a . Its properties have already been described, and 
we have only to notice some of its derivatives. Like water, 
the whole of its hydrogen may be replaced either by chlo- 
rine or by a metal. The direct action of chlorine decom- 
poses it; the hydrogen forms hydrochloric acid, and the 
nitrogen is set free in the form of gas ; but with a solution 
of a salt of ammonia, like the muriate or sal-ammonia, the 
action is different; the chlorine is slowly absorbed and a 
heavy yellow oil separates, which is a most dangerous com- 
pound, exploding with great violence by a gentle heat, by 
the contact- of phosphorus, fat oils, and many other sub- 
stances. It is composed of NC1 8 , and by the explosion is 
resolved into these elements. The name of chlorid ofnitro. 




gen has been given to it, but it is ammonia in which the 
hydrogen has been replaced by chlorine, and may be called 
trichloric ammonia. The action of iodine upon ammonia is 
more moderate than that of chlorine : if it is triturated with 
a solution of ammonia or mixed in an alcoholic solution, a 
black powder is obtained which explodes when dry by the 
slightest friction, but less violently than the chlorid. Its 
composition is NI a H, and it is therefore biniodic ammonia. 
The chlorine compound is indifferent to acids, but the 
iodic species still exhibits feebly basic properties: it is 
dissolved by dilute acids and precipitated again by a solu- 
tion of potash. 

682. When potassium is heated in ammoniacal gas, one 
equivalent of hydrogen is displaced, and an olive-green com- 
pound is obtained, which is N(H a K), and is decomposed by 
water into hydrate of potash and ammonia N(H a K)+H a O a 
■=(HK)O fl -f-NH 8 . When ammonia is passed over heated 
oxyd of copper, water is formed, and a compound which con- 
tains CugN. It corresponds to the red oxyd of copper, or oxyd 
of cuprosum cu 9 0g, and is Ncu s , or ammonia in which all the 
hydrogen has been replaced by cuprosum. It is formed at 
a temperature of 480° F., and is decomposed into its ele- 
ments with evolution of light at 540° F. 

683. The salts of ammonia next, claim our notice. Their 
characters and preparation, and the theory of ammonium 
have already been described, (518.) The mode of their 
formation is different from that of ordinary salts of metals : 
these, we have shown, whether the metals or their oxyds 
are employed, are produced by an equivalent substitution 
with the elimination of hydrogen or water, while ammonia 
and the acids unite directly to form salts, without the pro- 
duction of any second body. Thus ammonia and chlo- 
rohydric acid NH 8 -fHCl yield sal-ammoniac NH 4 G1; 
and sulphuric acid, which is bibasic and must be written 
2S0 3 .H a O a =S fl H a 8 , fixes directly 2NH 3 to form sulphate 
of ammonia. But these salts, notwithstanding their differ- 
ent mode of formation, are closely analogous to the salts 
of potassium and even isomorphous with them ; and while 
chlorid of potassium is KC1, the NH 4 in sal-ammoniac is 
perfectly similar in its relations to K ; and hence sal-ammo- 
niac is often regarded, not as the hydrochlorate. of ammonia 
NII 8 .IIC1, but as the chlorid of a quasi-metal } ammonium, 
which unites with 01 like potassium, and, like this metal, 




may even form an amalgam with mercury ; for (NH 4 )Hg 
evidently corresponds to KHg, and ZnHg. Ammonium, NH 4 , 
is then a group which, although it cannot be isolated, may 
replace hydrogen, and is equivalent to it. The neutral 
sulphate of ammonia is S a (NH 4 ) 3 O s , as sulphate of potash is 
S a (K a )0 8 , and the acid sulphate S a (H.NH 4 )0 8 , corresponding 
to S a (HK)0 8 . The group NH 4 may be represented by the 
symbol Am. 

684. The compound corresponding to a metallic oxyd in 
which NH 4 replaces H, like (KH)O a , probably exists in the 
aqueous solution of ammonia : it will be (NH 4 . H)O a or 
(AmH)O a ; but the ammonia is readily evolved by heat, the 
compound being like some salts of ammonia, very unstable. 
We shall see hereafter that there are homologues of ammo- 
nia which form more fixed combinations. A compound of 
(NHJgOa, or An^O^ corresponding to an anhydrous oxyd, 
is also possible ; like oxyd of zinc, (Zn a O a ,) it would evolve 
an equivalent of water in combining with an acid. 

685. In the same way that ammonia combines directly 
with acids it may unite with metallic salts ; for example, 
with chlorid of copper CuCl+NH 8 =(NH 8 Cu)Cl, and 
with sulphate of silver S a Ag a 8 +2NH s =S a (NH 8 Ag) a 8 : 
in these compounds one equivalent of hydrogen in the 
ammonia is replaced by copper and silver, and the groups 
may be designated cuprammonium and argentammontum. 
The white precipitate of mercury obtained by adding am- 
monia to a solution of chlorid of mercury is a body of this 
class, and is represented by (NH a Hg a )Cl : when this is 
boiled in a solution of sal-ammoniac, another compound is 
obtained, which is (NH s Hg)Cl. Here one and two equiva- 
lents of hydrogen are replaced by mercury. 

With the chlorid of platinum a similar chlorid is obtain- 
ed, which is known as the green salt of Magnus, and is 
(NH 8 Pt)Cl. But the group NH 4 may replace an equivalent 
of H in the last, and we have a salt described by Gros and 
Keiset, which is N(AmH a Pt)Cl or (N a H 8 Pt)Cl. Still another 
one has an equivalent of hydrogen replaced by CI, and is 
(N a H 6 ClPt)Cl. All of these correspond to chlorid of ammo- 
nium, and it will be observed that the sum of their atoms 
is always divisible by two. They combine with the oxygen 
acids like ammonia, and their sulphates, when decomposed b^ 
baryta, give the hydrated oxyds corresponding to (KH)O tf 




and, like it, caustic and alkaline. Cobalt and some other 
metals yields analogous compounds. 

686. The decomposition of ammoniacal salts to form water 
and am ids has already been alluded to, (654.) An ammo- 
niacal salt eliminates one equivalent of water for each equi- 
valent of ammonia which it contains, and the salt, if neutral, 
yields a neutral amid ; but if the salt is acid, that is, if a 
Dibasic acid has combined with one equivalent of ammonia, 
and has still an atom of hydrogen replaceable by a metal, 
this is preserved in the amid, which is then a monobasic acid. 
These compounds are often directly formed by the action of 
heat upon the several salts, and sometimes by distilling 
them with anhydrous phosphoric acid, which combines with 
the water. Amids may sometimes lose the elements of 
another equivalent of water, and form a class of bodies 
known as anhydrid amids, or nitryh. Acetate of ammonia 
C 4 H 4 4 +NH 8 =C 4 H 7 N0 4 — H 9 a =C 4 H 5 N0 fl , or acetamid, 
from which if H a O a be again abstracted; there remains 
acetonitryl C 4 H 8 N. 

687. Nitrous oxyd, which is NO, or rather N a Oa, is formed 
from nitrate of ammonia NHO e .NH 3 , by the abstraction of 
2H a O a , and is a true nitryl. Like all the other bodies of this 
class, it can reassume the elements of water and regenerate 
the acid and ammonia ; when passed over heated hydrate of 
potash, a nitrate is formed, ammonia escaping. 

Phosphoric acid forms not less than three anhydrid amids, 
corresponding to different salts of the different modifications 
of the acid. They are all white insoluble powders, which, 
under the influence of strong acids or alkalies, yield phos- 
phoric acid and ammonia. The one corresponding to nitrous 
oxyd is (PN)O a =P0 5 .NH 4 0-2H a O a . 

The points of interest with regard to the amids of the 
organic acids will be considered in their proper places. 

Carbonic Acid. 

688. This compound has already been described, but we 
again refer to it to speak of its equivalent, which, to corre- 
spond to those adopted for organic substances, must be writ- 
ten C a 4 in its anhydrous state. The gas fixes H a O a when 
it takes the acid form ; and carbonic acid, such as it exists 
in solution, is consequently C a H a 6 , in which one or both 
equivalents of hydrogen may be replaced by a metal, form- 




ing neutral and acid carbonates, or bicarbonates, as they are 
often called. . 

Carbonic acid is very readily separated from its aqueous 
solution, or decomposed into carbonic acid gas and water, in 
which it differs from more fixed bibasic acids, which some* 
times require a high temperature to effect such a division. 

689. Carbonic oxyd y which we write C fl 2 , is interesting 
from its action with chlorine in the formation of phosgene 
gas. It directly fixes 2C1 to form C a Cl a O a , which evidently 
corresponds to an hydrogen compound C 9 H a O. This group, 
Df which phosgene is the chlorinized species, is the prototype 
of an important class of organic compounds, the aldehydes 



690. Under this head is included a class of substances of 
vegetable origin, which agree in containing carbon with oxy- 
gen and hydrogen in the proportions which form water. 
When soluble, they are insipid, or have a sweet taste, and 
are generally nutritious. They are not volatile, and are 
readily decomposed by heat and many other agents. 

691. Sugars. — These bodies are soluble in water, have * 
sweet taste, and most of them by the process of fermentation 
yield alcohol and carbonic acid. 

Cane Sugar , C^H^O^. — This occurs in the juices of 
many plants, as the sugar-cane, maple, beet-root, and Indian 
corn. It is obtained by evaporating the juice to a syrup, 
when the sugar crystallizes in grains of a brownish color, 
and is rendered pure and white by redissolving it, and filter- 
ing the solution through animal charcoal, (337.) By the 
slow evaporation of a concentrated solution, it is obtained 
in fine transparent crystals, which are derived from an oblique 
rhombic prism ; in this state it constitutes rock-candy. It 
fuses at 356°, and forms, on cooling, a vitreous mass well 
known as barley sugar : this gradually becomes opaque and 
ehanges into a mass of small crystals of ordinary sugar. 
Sugar is soluble in about one-third its weight of water, form- 
ing a thick syrup. It is insoluble in pure alcohol. 

692. Grape Sugar; Glucose, C^H^O^ + 2H 9 O fl .— This 
sugar is found in the grape and many other fruits, and in 
honey. It is formed when cane sugar or starch is boiled with 
dilute sulphuric acid, and is a product in many other trans- 





formations. The urine in the disease called diabetes meUitou 
contains a large quantity of grape sugar, which is formed 
from the starch and similar substances taken as food. 

Grape sugar is generally obtained as a white granular 
mass, which requires one and a half parts of cold water to 
dissolve it : it is less sweet to the taste than cane sugar, and 
about two and a half times as much are required to give an 
equal sweetness to the same volume of water. When heated 
to 212°, the two equivalents of water are expelled. With 
sulphuric acid, grape sugar forms a coupled acid, the sul- 

Ehosaoohario. It forms with chlorid of sodium, a crystal- 
ne compound, which is C^H^O^.NaCl.HgOj,. The water 
is lost by heat If a solution of grape sugar is mixed with 
a solution of potash, and then with a little sulphate of copper, 
the liquid becomes dark, and soon deposits suboxyd of copper 
in the form of a red powder ; cane sugar yields no precipi- 
tate until the solution is boiled. This test enables us to detect 
the jffitro part of grape sugar in a liquid. Honey is a mix- 
ture of crystallizable grape sugar, with an uncrystallizable 
syrup identical with it in composition. 

693. Sugar of Milk; Lactose, C S4 H 9? O 90 +2H il O Jl .— This 
is found only in the whey of milk, and is obtained by evapo- 
rating it, and purifying the product- by crystallization. 
Lactose forms semi-transparent prisms, soluble in six parts 
of cold water, and two and a half of boiling water ; it is 
much less sweet than cane or grape sugar. By a heat of 
212° its water is expelled ; when boiled with dilute sulphuric 
acid, it combines with the elements of two equivalents of 
water, and is converted into grape sugar. 

Mannite, C^H^O^. — This substance is not properly a 
sugar, as it does not contain oxygen and hydrogen in the 
proportions to form water, and is not susceptible of fermenta- 
tion. It exists in the juice of celery and many sea- weeds, 
and constitutes the principal part of the manna of the shops, 
which is the concreted juice of a species of ash-tree. When 
this is dissolved in hot alcohol, mannite is deposited on 
cooling in delicate silky crystals, which are sweet, and very 
soluble in water and alcohol. 

Mannite dissolves in a mixture of fuming nitric and sul- 
phuric acids, and water precipitates from the mixture a 
white matter, insoluble in water, which may be crystallized 
by dissolving in hot alcohol. It is formed by the fixation of 
the elements of nitric acid and the elimination of those of 




water, and is represented by C lfl H 8 N 6 38 . We may repre- 
sent N0 4 as replacing hydrogen, and designate it by X 
The new compound, which is called nitro-mannite, will be 
then C^H^NO J e O M = O^Xfi^ This mode of notation 
is convenient, but, agreeably to the views laid down in the 
introduction, we must suppose successive substitutions, in 
the first of which C^H^O^ — HO a replaces H in nitric acid 
NH0 8 , yielding N^C^H^O^O,, and H ? O a ; this product 
then reacts with a new equivalent of nitric acid, and so on. 
From the large portion of oxygen which it contains, nitro- 
mannite is very combustible, and it explodes spontaneously 
when struck with a hammer. 

Products of the Decomposition of the Siigars. 

694. The Vinous Fermentation. — When the juice of grapes 
or other fruits containing sugar is exposed to the air, a pecu- 
liar decomposition ensues, in which the sugar is resolved 
into carbonic acid gas and alcohol. A solution of pure 
sugar is not changed by exposure to the air ; but if there is 
added to it a little yeast, or the juice of any fruit in the state 
of fermentation, decomposition takes place, and carbonic acid 
and alcohol are formed. Many substances besides yeast will 
effect this change, as blood, albumen, or flour paste in a state 
of decomposition. It appears that the influence of a fer- 
ment depends on the condition rather than on the kind of 
matter. Any nitrogenized substance capable of undergoing 
putrefaction produces the same effect, and we are to attribute 
this change in the juice of fruits, to a small portion of albu- 
minous matter present. The mode in which these substances 
act is not understood, but it is supposed that when in a state 
of decomposition, they are able to induce a similar state in 
other substances with which they are in contact; the equi- 
librium of the atoms in the compound is thus disturbed, and 
the elements arrange themselves in new forms. 
It is interesting to know that the fermentation 
of sugar takes place only in immediate contact 
with the ferment. This is readily shown, as in 
figure 402, by placing a solution of sugar in the 
bottle A, and some beer yeast in the tube 
ab f the lower end of which is covered with 
porous paper. The sugar solution passes 
through the paper into the tube, where an 
active fermentation is set up with an abundant Fig. 402. 




evolution of carbonic acid. Meanwhile no change occurs in 
the solution in the bottle, which may be preserved unaltered 
for any length of time. 

695. The act of fermentation is always accompanied by 
the appearance of a peculiar microscopic vegetation, which. 
is formed when solutions containing albuminous matters 
are abandoned to putrefaction. The solution becomes tur- 
bid, and a gray deposit is gradually formed in it, consisting 
of ovoidal bodies variously grouped, whose development has 
been carefully studied under the microscope. Figures 403 
to 407 show the various stages of this fungus growth. The 


Fig. 403. Fig. 404. Fig. 405. Fig. 406. Fig. 407. 

original globule (1) A, fig. 403, in about six hours produces 
another, (2,) fig. 404, B, like itself; the two again each 
germinate a third, as seen at 3, C and D, fig. 405 ; and in 
like manner the germination proceeds, as in E, (4,) fig. 406, 
until, in about three days, thirty globules are formed about 
the original cell. The development then ceases. The se- 
veral globules are coherent, but appear to be distinct and 
complete in themselves. 

696. The conversion of grape sugar into alcohol and car- 
bonic acid is very simple : one equivalent of dry grape sugar 
CjJB^O^ divides so as to form four equivalents of alcohol 
and four of carbonic acid gas. 

4 equivalents of alcohol 4XC 4 H,0 a =» C^H^O, 

4 " of carbonic acid gas 4 X C 9 4 — C, O^ 

1 " of grape sugar = C^H^O^ 

Grape sugar is the only kind which is capable of this fer- 
mentation ; and, although the others readily yield alcohol 
and carbonic acid, it is found that the first effect of the fer- 
ment is to transform them into grape sugar, by the assimila- 
tion of the elements of water. 

697. Weak alcoholic liquors often become acid when 
exposed to the air, from oxydation of the alcohol and the 
formation of acetic acid ; but this acid is sometimes directly 



LACTIC ACID. \C 4<0§ l 

formed from the decomposition of the sugar, independent of 
the action of the air, and is the cause of the souring of such 
wines as contain considerable sugar, but are very weak in 
alcohol. If a solution of sugar is mixed with cheese curd 
and exposed for some weeks to a temperature of about 68° F., 
the air being excluded, it becomes acid, and a portion of the 
sugar is converted into acetic acid C 4 H 4 4 . An equivalent 
of grape sugar contains the elements of six equivalents 
of this acid. The presence of cheese curd under condi- 
tions modified by temperature and the presence of earthy 
bases, causes other fermentations and different results. At 
a temperature of from 95° to 104° F. the products are 
lactic acid C^H^O^, and a viscous substance analogous 
in composition to sugar. Such a decomposition takes place 
in the juices of beets and carrots at a high temperature, and 
has been called the viscous fermentation. Mannite some- 
times appears as a secondary product. If carbonate of lime 
is added to saturate the lactic acid as soon as formed, the 
decomposition proceeds at a lower temperature, and the 
lactate of lime is almost the only product. An equivalent 
of crape sugar C^H^O^ breaks up into two equivalents of 
lactic acid C^H^O^. 

698. The action of the curd of milk in a more advanced 
state of decomposition gives rise to the vinous fermentation : 
milk at the ordinary temperature becomes sour from the 
conversion of its sugar into lactic acid, but when kept at 
about 100° the grape sugar at first formed is converted into 
alcohol and carbonic acid gas. In this way the Tartars pre- 
pare a spirit from mare's milk; an elevated temperature 
promotes the decomposition of the curd and enables it to 
effect this transformation. 

699. Lactic Acid, C^H^O^. — This acid may be obtained 
from sour milk, but is more easily prepared by the fermenta- 
tion of sugar with caseine. Fourteen parts of cane sugar are 
dissolved in sixty of water ; to the solution is then added 
four parts of the curd from milk, and five parts of chalk to 
neutralize the acid as it is formed. This mixture is kept 
at a temperature of 80° to 95° F. for eight or ten days, or 
until it becomes a crystalline paste of lactate of lime. This 
Is pressed in a cloth, dissolved in hot water, and filtered ; 
the solution is then concentrated by evaporation. On cool- 
ing, it deposits the salt in crystals, which may be purified 
by recrystallization. The lactate of lime may be uccom- 




posed by the careful addition of oxalic acid, which precipi- 
tates the lime, and the solution of lactic acid thus obtained 
is concentrated by evaporation, and purified by solution in 
ether. It is a syrupy liquid, of specific gravity 1*215, and 
is strongly acid to the taste. 

700. When lactic acid is heated to 482°, a white crystal- 
line substance sublimes, which is called lactide: it is derived 
from the acid by the abstraction of the elements of two equi- 
valents of water, and has the formula C^HgOg. It is soluble 
in alcohol, but scarcely soluble in water : by long continued 
boiling with it, however, it is converted into lactic acid. 
This acid is bibasic, and its salts are generally soluble and 
crystallizable. The lactate of lime C^H^Ca^O^ crystallizes 
in fine prisms, with six equivalents of water. The lactate 
of zinc is obtained by decomposing a hot concentrated solu- 
tion of lactate of lime by chlorid of zinc : the salt crystallizes 
in cooling in beautiful colorless prisms. The lactate of iron 
C^H^FegO^ is sparingly soluble in cold water, and may be 
prepared by a similar process : it is employed in medicine. 
A double lactate of lime and potash, and acid lactates of lime 
and baryta have been obtained ; the latter is C^H^BaX)^. 
If the crystalline paste of caseine and lactate of lime is kept 
for some time at a temperature of about 95°, the salt gradually 
redissolves, hydrogen and carbonic acid gases escape, and 
when, after a few weeks, this new fermentation has sub- 
sided, there remains only a solution of the lime salt of a 
new acid, butyric acid, C 8 H s 4 . In this butyric fermentation, 
the lactic acid is decomposed into carbonic acid, hydrogen 

•and the new acid, C lfl H M ls = 2C a 4 + 2H a +C 8 H 8 4 . 

701. Under certain circumstances not well understood, 
there appears as an accessory product to the vinous ferment- 
ation, an oily liquid, which is homologous with alcohol and 
has been named amylol. It is represented by C^H^O,,, and 
is supposed to be formed from sugar by a process which 
may be called the amylic fermentation, in which, as in the 
butyric, hydrogen and carbonic acid will be disengaged. 

The action of dilute nitric acid with cane or grape sugar 
yields saccharic acid C^H^O^, which is bibasic : strong 
nitric acid converts sugar into oxalic acid, and chromic acid 
into formic acid. All of these derivatives will be described in 
their proper places. 

702. When sugar is added to a concentrated solution of 
three times its weight of hydrate of potash, and heated, the 



STARCH. 407 

mixture becomes brown, and hydrogen gas is evolved. When 
the action ceases and the mass is cooled, dissolved in water* 
and distilled with dilute sulphuric acid, it yields formic and 
acetic acids, with a new acid, the metaeetonic, which is 
obtained as a volatile liquid, with a pungent acid odor. It 
is monobasic, and has the formula 8 H 6 4 . 

A mixture of sugar and quicklime, when distilled, affordf 
acetone and an oily liquid called metacetone which yields 
metaeetonic acid when distilled with a mixture of bichromate 
of potash and sulphuric acid. Mannite, starch, and gum 
afford the same results with hydrate of potash and lime. 

703. Gum, C^HjjoOao.— This substance is best known in 
gum arable : the gums which exude from the cherry and 
plum, the mucilage of flaxseed, and of many other plants, 
are identical with it. Gum is soluble in water, and forms a 
viscid solution, from which alcohol precipitates it unchanged. 

When boiled with dilute sulphuric acid, it is converted 
into grape sugar. With nitric acid, gum and lactose yield 
the mucic acid, which distinguishes them from all the other 
bodies of this class. The mucic acid is a white crystalline 
powder, which is sparingly soluble in water : it is bibasic, 
and is represented by the formula C^H^O^. It is conse- 
quently metameric with the saccharic acid, although quite 
different in its properties. 

704. The pectic acid, which is extracted from many 
fruits, appears to be nothing but a modified form of gum, 
and yields grape sugar with dilute acids. It combines with 
lime and some other bases to form compounds, which have 
been described as pectates. Both gum and sugar have also 
the property of exchanging one or two equivalents of hy- 
drogen for lead, barium, or calcium, to form similar com- 

705. Starch, C^H^O^. — This substance exists in a great 
variety of vegetables. It is found iu all the cereal grains, 
in the roots and tubers of many plants, as the potato, and 
in the bark and pith of various trees. It is obtained by 
bruising wheat and washing it in cold water, which holds the 
starch in suspension, and deposits it on standing. Potatoes 
furnish a large portion of starch by a similar process. The 
substances known as arrow-root, salep, sago, and tapioca, 
are varieties of starch, obtained from different plants, and 
sometimes altered by the heat employed in drying. 

When examined by the naked eye it is a white shining 


by Google 


powder, but under the micro- 
scope is seen to consist of irregu 
lar grains, which have a rounded 
outline, and are composed of 
concentric layers, covered with 
I _ an external membrane. The 
"cy? diameter of the grains of potato 
starch is about 3 fa of an inch. 
g^ |^^ ^S^jfflEfr Starch is insoluble in cold 
^•rfe • 5$ <^%Rln water, but if the mixture is 
Tf f§ ^J^P' heated, the globules swell, burst 
Fi 408 their envelopes, and form a 

transparent jelly, which is cha- 
racterized by producing a deep blue color with a solution 
of iodine. 

When the solution of starch is mixed with a little acid, or 
an infusion of malt, and gently heated, it becomes very fluid, 
and is changed into dextrine.* This has the same com- 
position as starch, but is very soluble in cold water, and is 
not colored blue by iodine. If starch is heated to 300° or 
400°, it is rendered soluble in water, and possesses all the 
properties of dextrine. In this state it is used in the arts as 
a substitute for gum, under the names of British gum and 
leiocome. When dextrine is boiled for some time with 
dilute sulphuric acid, it is converted into grape sugar. It 
has been mentioned that grape sugar is formed in this way 
from starch ; but its formation is always preceded by that 
of dextrine. One part of starch may be dissolved in foul 
parts of water, with about one-twentieth of sulphuric acid, 
and the mixture boiled for thirty-six or forty hours. The 
liquid is then mixed with chalk to separate the acid, and by 
evaporation and cooling affords pure grape sugar. Oxalic 
acid may be substituted for the sulphuric, with the same 
result. Starch sugar is extensively manufactured in Europe, 
and is often used to adulterate cane sugar. In this process 
the starch combines with the elements of two equivalents of 
water, C a4 H 20 20 +2H a O a =C S4 H 94 0, M : the acid is obtained 
at the end of the process quite unaltered, and one part of 
acid will saccharify one hundred of starch by long continued 
boiling. Starch or dextrine unites with sulphuric acid to 

* So named, because when a beam of polarized light is passed through 
the solution, it causes the plane of polarization to deviate to the right 





form a coupled acid; and it is probable that this is first 
formed and then destroyed by boiling : at the moment of 
decomposition, the liberated dextrine takes up the elements 
of water necessary for the formation of sugar. A small 
portion of the coupled acid is always found in the solution. 
706. The action of an infusion of malt upon sugar is 
peculiar: this substance is prepared from barley, by 
moistening the grain with water, and exposing it to a gentle 
heat till germination takes place, when it is dried in an oven 
at such a temperature as to destroy its vitality. The grain 
now contains a portion of starch sugar, and a small portion 
of a substance called diastase,* to which its peculiar proper- 
ties are due. It is precipitated by alcohol from a concen- 
trated infusion of malt, as a white flaky substance, which 
contains nitrogen, and is very prone to decomposition. When 
a little diastase is added to a mixture of starch and water, 
at a temperature of from 130° to 140°, the starch is soon 
converted into dextrine, and in a few hours into grape sugar. 
The action of an infusion of malt is due solely to the presence 
of a minute portion of this substance, one part of which will 
convert two thousand parts of starch into sugar. This effect 
appears to be due to a peculiar state of the diastase, which is 
a portion of the azotized matter of the grain in a modified 
form, and is analogous to the ferments, already alluded to. 

707. Woody Fibre; Cellulose, C^ 
is the solid insoluble part of vege- 
tables, and remains when water, 
alcohol, ether, dilute acids, and al- 
kalies have extracted from wood 
all its soluble portions. It is 
nearly pure in cotton, paper or old 
linen. The tissue of vegetables 
is formed principally of cellu- 
lose. The cellular tissue is seen 
almost pure, constituting the cell 
walls of young plants. These cells 
arc sometimes spherical, or rounded 
in form. In other cases the 
woody tissue forms oblong cells, 
communicating by their extre-ni- 

Am,. — This substance 

Fig. 409. 

♦From the Greek diistemi, to separate, because it separates the 
insoluble envelopes of the starch globules. 





ties, as seen in figure 409, which is a section of aspara* 
gas, and also in figure 410, which shows a fibre of flai 
much magnified. The cellulose in this form receives 
whe name of vascular tissue. In the course of time the walls 
of the cells become lined with an incrusting matter, which 
grows thicker with the age of the plant, finally leaving 

only minute 
pores or con- 
' duits for the 
circulation of 
Wg.«o. the sap. This 

incrusting matter which forms a part of ordinary wood, is 
named lignin. It is chemically different from cellulose, 
but has been little studied. Figure 411 shows the structure 
of wood as seen in the transverse section of a piece of oak, 
under the microscope. The black spaces are the ducts, 

for the circulation of the 
sap, of which a a a are re- 
markable examples. The 
white lines mark the outline 
and comparative thickness 
of the original cells, such as 
are seen in the vertical sec- 
tion of asparagus, fig. 409. 
These have been filled with 
lignin, which is more dense 
and hard near the centre of 
the tree than at the exterior. 
The albuminous matters, 
Fig. 411. which are the principal 

cause of the decay of wood, are also more abundant in the 
outer than in the inner cells. The coloring and resinous 
matters are deposited with the incrusting material. 

Cellulose is identical in composition with starch and dex- 
trine, and by the action of strong sulphuric acid is dissolved 
and converted into that substance. This experiment is easily 
made with unsized paper or cotton : to two parts of this, 
one part of the acid is very slowly added, taking care to 
prevent an elevation of temperature, which would char the 
mixture. In a few hours the whole is converted into a soft 
mass, which is soluble in water, and is principally dextrine. 
If the mixture is now diluted with water and boiled for three 
or four hours, the dextrine is completely converted into 




grape sugar, which is obtained by neutralizing the acid with 
chalk, and evaporation. By this process paper or rags will 
yield more than their weight of crystallizable sugar. 

708 The mutual convertibility of these different sub- 
stances is interesting in relation to many of the phenomena 
of vegetable life. The starch in the germinating seed is 
changed by the action of diastase into sugar, in which so- 
luble form it seems better fitted for the nourishment of the 
embryo plant. In the growth of this, we have an example 
of the formation of cellulose from sugar, in which this 
substance assumes a structural form under the action of the 
vital force. This is a transformation from the unorganized 
to the organized, which mere chemical affinity can never 

709. Many unripe fruits, as the apple, contain a large 
quantity of starch, but no sugar. After the fruit is fully 
grown, the starch gradually disappears, and in its place we 
find grape sugar. This change constitutes the ripening of 
frnits, and, as is well known, will take place after they 
are gathered. In this process we have clearly a conversion 
of the starch into sugar, by the agency of the vegetable 
acids present in the fruit — a change which is the reverse of 
the previous one, and is probably independent of life. 

710. Xyloidine, Pyroxyline. — The action of strong nitric 
acid upon starch yields a compound very similar to nitro- 
mannite, which is insoluble in water and very combustible : 
if we represent N0 4 by X, the formula of this body, to 
which the name of xyloidine has been given, will be 
C M R s ^Kfl ao =Q a§ EL t ^fi jm . With sugar a similar sub- 
stance may be formed. 

The action of strong nitric acid, or a mixture of nitric 
and sulphuric acids, upon woody fibre, such as paper, cotton, 
or sawdust, gives rise to an interesting substance, which has 
been named pyroxyline, or gun-cotton, as that form of cellu- 
lose yields the purest product. The following is an outline 
of the process : — one hundred grains of clean cotton are im- 
mersed for five minutes in a mixture of an ounce and a half 
of nitric acid of specific gravity 145 to 1-5, with the same 
measure of strong sulphuric acid ; it is then removed, care- 
fully washed in cold water from every trace of acid, and 
dried at a temperature which should not exceed 120°. As 
thus prepared, it preserves the form of the cotton unaltered, 
but has less strength than the original fibre. Jt inflames 




by a very gentle heat : sometimes, under circumstances sot 
well understood, it has been observed to take fire at 212° F. 
Its combustion is instantaneous, accompanied by an immense 
volume of flame, and it leaves not the slightest residue. 
When ignited in a confined space it explodes with great 
violence: one-tenth of a grain is sufficient to shatter the 
strongest glass tube. Its power in propelling balls is about 
eight times greater than that of gunpowder; its tremendous 
energy depends upon the fact that it is completely resolved, 
by its combustion, into aqueous vapor and permanent gases, 
which are carbonic ozyd, carbonic acid, and nitrogen. As 
these are much less noxious than the gases resulting from 
the combustion of gunpowder, the gun-cotton will be found 
of great use in mining. Its composition is analogous to 
that of nitro-mannite. There appear to be two species, one 
of which is soluble in a mixture of alcohol and ether, and 
the other insoluble; both are generally present in gun- 
cotton. They are substitution products from cellulose, and, 
representing N0 4 by X, the insoluble form is C^H^X^O,^ 
and the soluble C^H^X^ = C^HJtf.O^. It will be 
seen that they are formed from the action of nitric acid with 
the elimination of H a O, for each equivalent of the add. 
Thus, C^H^+GNHOe = O^HJK.O^+eH.O,. 

The ethereal solution dries rapidly and leaves a tenacious 
transparent film of pyroxyliue : it is used in surgery for 
covering wounds and abraded surfaces from the air, and is 
known by the name cf collodion. 

Transformation of Woody Fibre. 

711. By the action of atmospheric air and moisture, wood 
undergoes a slow decay, dependent on the absorption of oxy- 
gen, to which Liebig has applied the term eremacausis.* 
The carbon is converted into carbonic acid, while the oxygen 
and hydrogen of the lignine unite to form water. The re- 
sidue is still found to contain oxygen and hydrogen in the 
original proportions, but the relative amount of carbon is 
continually increasing. For each equivalent of carbonic 
acid two of water are evolved. The final result of this pro- 
cess is a brown or black residue, which constitutes vegetable 

* From erema, slow, and kausis, combustion, a term by which that 
chemist denotes those changes which take place in organic bodies from 
the gradual action of oxygen. 




mould. Different products of this decomposition have been 
described under the names of humus, geine, ulmine, hutnic 
and ulmic acids. 

Nearly all of these bodies contain ammonia, for which 
they have a strong affinity : this is in part absorbed from 
the air, but the experiments of Mulder seem to show that 
they have the power of forming ammonia from the nitrogen 
of the atmosphere. Pure humic acid moistened and placed 
in a close vessel filled with air, is found after some months 
to contain a considerable quantity of ammonia. The hydro- 
gen, evolved by a slow decomposition of the water, is brought 
into contact with nitrogen under such conditions that they 
combine and produce the alkali. 

712. The decomposition of wood, when buried in the 
ground and excluded from the action of the air, is very dif- 
ferent The oxygen which it contains gradually combines 
with the carbon to form carbonic acid, and substances are 
obtained in which the proportion of carbon and hydrogen 
is greater than in the original fibre. Peat, lignite, and bitu- 
minous coal are products of this decomposition. The car- 
bon and hydrogen in coal combine in various ways, and 
often generate vast quantities of gaseous carburets of hydro- 
gen, (450.) Anthracite has resulted from the action of heat 
on bituminous coal, which has expelled all the volatile in- 
gredients, and left a residue of nearly pure carbon. 

Destructive Distillation of Wood. 

713. The principal products of the decomposition of wood 
by heat are carbonic acid gas, water, and gaseous carburets 
of hydrogen . With the water are mixed several other bod ies, 
among which are acetic acid and pyroxylic spirit, presently 
to be described, and a quantity of oily, tar-like substance, 
containing several interesting bodies, which we shall mention. 
These products are obtained on a large scale by distilling 
wood in iron cylinders ; the quantity of acetic acid is so 
considerable that the process has become important in the 

Kreasote. — This substance occurs dissolved in the crude 
acetic acid from wood, and is separated and purified by 
a complicated process. It is a colorless oily fluid, which 
boils at 397°, and has a specific gravity of 1037. It has a 
peculiar and very persistent odor, resembling that of smoke, 
and % powerful burning taste. It is soluble in about 100 




parts of water, and the solution possesses powerful antiseptic 
qualities. Meat which has been soaked in it is incapable 
of putrefaction,* and acquires a delicate flavor of smoke. 
The power of wood-smoke to preserve flesh is due to the 
presence of kreasote. It is a corrosive poison when taken 
in any quantity, but a dilute solution is used medicinally, 
both internally and externally, as a styptic and antiseptic. 
The composition of kreasote is C 14 H 8 8 . It combines with 
the alkalies to form crystalline compounds. 

714. Wood4ar contains several carburets of hydrogen, one 
of which, called eupion, is an oily, fragrant liquid, of the 
specific gravity '655, being the lightest liquid known. Its 
formula is, probably, C 6 H 6 . 

Paraffin. — This is a white crystalline substance, obtained 
from the less volatile portions of wood-tar. It crystallizes 
in delicate needles, which fuse at 110° ; it is soluble in alco- 
hol and ether. Its formula is C^H^. Paraffin is obtained 
in large quantities by the dry distillation of beeswax. 

715. Coal-tar consists principally of a mixture of various 
hydrocarbons; some of these are liquid and very volatile, 
constituting what is called gas naphtha. Among the less 
volatile products are two solid carburets of hydrogen, naph> 
thalen, and paranaphthalen, or anthracen. The first of these 
is formed by the decomposition of many organic matters 
by heat. Its formula is C^Hg : it is volatile, and forms 
beautiful pearly crystals of a fragrant odor. The action of 
chlorine, bromine, and nitric acid on naphthalen, gives rise 
to a great number of compounds. They are formed by suc- 
cessive substitutions of the hydrogen by one or more of these 
substances, and many metameric modifications of these bodies 
exist. Thus, the bichlorinized naphthalen C^Bed,, occurs 
in seven modifications, which are perfectly distinct in their 
characters. We are led to suppose that these compounds 
owe their different properties to a different arrangement of 
their constituent atoms, and it is easy to see that, in this 
way, the number of possible combinations will be immense. 
More than twenty substances have been described, in which 
chlorine is in part substituted for the hydrogen of the naph- 
thalen. The final product of the action of chlorine is C^Clg, 
being a chlorid of carbon, which preserves the type of naph- 
thalen. In addition to these, coal-tar contains a consider. 

* Hence the name, from the Greek kreaa, flesh, and aoto, I preserve. 

Digitized by VjOOQ IC 


able proportion of a body named phenol, and several organic 
alkaloids. The watery products of the distillation of coal 
hold a large quantity of ammonia in solution, often combined 
with hydrosulphuric and hydrocyanic acids. 

716. Petroleum. — In many parts of the world an oily 
matter exudes from the rocks, or floats on the surface of 
springs. The principal sources of this substance are Amiano 
in Italy, Ava, and Persia, but it is found in many places in 
our own country. The well-known Seneca oil is an instance 
of this kind. Petroleum is a variable mixture of several 
bodies. By distillation, it yields a colorless liquid, called 
naphtha, which is very light, volatile, and combustible. Its 
formula is, probably, C ia H 10 . Naphtha occurs nearly pure 
in Italy and Persia, and is used for illumination. 

Petroleum contains a variety of other bodies, among which 
are paraffin, and several resinous matters, formed, perhaps, 
by the oxydation of naphtha. These substances are pro- 
bably derived from coal or other matters of vegetable origin. 


717. This series of compounds has already been alluded to 
in explaining the principle of homology. The alcohols may 
be represented by C n H„4_ a a , n being a number divisible 
by two: all of them by oxydizing agents lose H a and 
combine with O fl to form monobasic acids, whose general 
formula is C n H n 4 . Of these acids we have now nearly a 
complete series up to the stearic acid, in which n=38. 
But a few of the corresponding alcohols are known ; the 
principal are methol C a H 4 a , wine alcohol C 4 H 8 O a , ami/lie 
alcohol oxamyhl C 10 H ia O a , and cetic alcohol or cetol CgaH^Oj,. 
We shall first describe the alcohol of wine, to which we 
may conveniently give the name of vinol : it is the best 
known and most important of the series, and will serve to 
illustrate the history of the others. 

Vinol — Common Alcohol, C 4 H 6 a . 

This substance has long been known under the name 
of alcohol, or spirits of wine. We have already explained 
the manner in which it is obtained as a result of the fer- 
mentation of sugar. The vinous fermentation in the juice of 
the grape and -other fruits, in an infusion of malt, or in the 





syrup of the sugar-cane, always results in the conversion of 
the sugar which it contains, into alcohol and carbonic acid 
gas. When the fermentation is arrested before all of the 
sugar is decomposed, the wine is sweet; if the liquor is 
bottled before the action is finished, the excess of carbonic 
acid remains in solution, and gives an effervescent and spark- 
ling property, as in bottled beer and champagne. 

When these fermented liquors are distilled, the alcohol, 
boiling at a lower temperature than water, passes over 
first. By repeated distillation in this way, a liquid is 
Obtained which contains 85 parts of alcohol in 100. To 
obtain it free from water, it is digested with quicklime, or 
better with fused chlorid of calcium, which combines with 
the water. The mixture is then distilled in a water-bath, 
and pure alcohol passes over. A convenient apparatus for 
condensing the vapor of alcohol, ethers, and other volatile 
substances, is shown in figure 412. - / 

Fig. 412. 

The retort r is connected with a glass condensing tube t, 
about which a metallic tube m is secured by corks at the ends, 
leaving a water-tight space between the two. A funnel tube 
/ conducts cold water from the tank w to the lower end of 
the condenser. This escapes at the upper orifice o, thus 
maintaining a constant current of cold water, by means of 
which the vapors of even very volatile liquids are easily 

718. Pure or absolute alcohol is a colorless fluid, with a 
specific gravity of about -800, and boils at 173° F. Its den- 




sity vanes very much with its temperature, (102 ;) thus at 
82° it is 0-815; at 50°, -8065; at 59°, -8021; at 68°, -7978; 
and at 77°, -7933. It has a pungent and agreeable taste 
and a fragrant odor. It is very combustible, and burns 
with a pale blue flame without smoke, which renders it very 
useful as a source of heat in chemical processes. The action 
of alcohol on the system is well known as that of a power- 
ful and dangerous stimulant. It is largely used in the 
operations of the arts, the preparation of medicines, and the 
processes of chemistry. Its solvent powers are very great : 
the volatile oils and resins are dissolved by it, as well as 
many acids and salts, the caustic alkalies, and a large num- 
ber of other substances. . 

The density of alcohol vapor is 1589 # 4, and its equivalent 
is represented by four volumes, oxygen being one volume ; 
thus — 

4 volumes of carbon vapor. 4X 829. as 3316*0 

12 " " hydrogen 12 X °>2 = 830-4 

2 " "oxygen 2XH05-6 ss 2211-2 

Equal 4 volumes aloohol vapor, of which 1 volume weighs.... 1598*4 

719. Pure alcohol dissolves several salts, as the chlorid 
of calcium and the nitrates of lime and magnesia, and forms 
with them crystalline compounds, in which the alcohol takes 
the place of the water of crystallization, by virtue of the 
homologous relation which it sustains to water. When potas- 
sium is added to alcohol free from water, hydrogen is evolved 
and a crystalline compound formed, in which the metal 
replaces hydrogen. It is C 4 H 5 K0 3 , and by the action 
of water is decomposed into alcohol and hydrate of potash, 
C 4 H 5 K0 9 +H fl fl == C 4 H 6 fl -f(KH)0 a . By an indirect pro- 
cess, a compound is obtained in which the oxygen of alcohol 
is replaced by sulphur, and which is C 4 H 6 S a . It is a colorless 
very volatile liquid, having a strong odor resembling that of 
onions. Like the oxygen species, it may exchange H for a 
metal ; with oxyd of mercury it forms water and a crystal- 
line compound C^^jHgSj : from the violence of the action 
it has received the fanciful name of mercaptan, (from mer- 
curium captans!) 

Action of Acids upon Alcohol. 

720. It has been shown that when n in the general 
formula of the alcohols becomes equal to zero, we have 





water 11,0,, which may be regarded as their homologue and 
prototype. We have farther pointed out the fact that a 
group of elements is often found to be equivalent to an atom 
of hydrogen, and capable of replacing it in combination: 
such is NH 4 in the ammonia salts; and in the compounds of 
vinic alcohol, the group C 4 H 5 will be found to sustain simi- 
lar relations. In water, which is (HH)O a , one atom of 
hydrogen may be replaced by this group, and we have then 
(C 4 BL.H)0 t , which is alcohol. In the potassium compound 
just described, the second atom of hydrogen is replaced by 
ft metal, and we shall presently describe a compound in 
which both atoms of the hydrogen are replaced by the 
organic group: it is (C.H 5 .C 4 H s )0 s =C 8 H 10 a . This 
same group may also replace the hydrogen in acids; a 
monobasic acid reacts with one equivalent of alcohol and 
eliminates an equivalent of water, forming a compound in 
which C 4 H 5 replaces H in the acid, and renders it neutral. 
Such compounds are called ethers of the various acids. 
With bibasic and tribasic acids, two and three equivalents 
of alcohol combine to form neutral ethers, and eliminate two 
and three equivalents of water. But when a bibasic acid re- 
acts with but one equivalent of alcohol, only one atom of its 
hydrogen is replaced, and the second atom remains as be- 
fore, capable of being exchanged for a metal. Such com- 
pounds are acid ethers or vinic acids. 

721. Although the ethers are thus analogous to salts in 
their constitution, they are less readily decomposed than the 
corresponding metallic salts ; they frequently require the aid 
of heat to effect the breaking up of the combination, and are 
generally more stable as their equivalent is more elevated. 

The neutral ether containing sulphuric acid, for example, 
does not precipitate salts of baryta, and the corresponding 
vinic acid forms a soluble saTt with that base. In these, 
and many other instances, the properties of the acids seem 
masked in their ethers, but similar cases are met with in 
the salts of inorganic bodies. 

722. The action of chlorohydric acid, and other acids 
containing no oxygen, upon alcohol, requires a little explana- 
tion. We have seen that when HC1 acts upon a metal, the 
compound eliminated is of the type H a ; but when the hy- 
dracid acts upon a hydrated oxyd, as (KH)O fl , the same 
chlorid is formed, and H a 3 is evolved ; so it is with al- 
cohol, which with hydrochloric acid yields water and a body 



ETHERS. 419 

C 4 H S 01. As C 4 H 5 is equivalent to H, the new ether repre- 
sents chlorohydric acid, and is evidently the chlorinized 
species of a hydrocarbon C 4 H 6 , which should yield with 
(Cl 9 ) the same product, as a result of direct substitution. As 
water H fl O s is the prototype of the alcohols, so (H fl ) is the 
prototype and homologue of the carbohydrogens like C 4 H a , 
whose formula is C w H w+9 =C n H n -|-H jl ; and chlorohydric 
acid HC1 is the type of the chlorohydric ethers. 

As the ethers of alcohol contain C 4 H 6 , replacing H in 
the acids, and consequently differ from the latter by (C fl H 3 ) fl , 
it follows that the ethers are always homologous with their 
parent acids. 

In describing these compounds, we shall often designate 
the group C 4 H 5 by the symbol Et, and write alcohol (EtH)O a . 


723. Chlorohydric Ether, C 4 H 5 C1 = EtCL— When alcohol 
is saturated with chlorohydric acid gas, and heated, it is con- 
verted into water and this ether, (EtH)O a +HCl = EtCl + 
H s 9 . By distillation it is obtained as a pungent aromatic 
liquid, slightly soluble in water, and boijing at 52° F. : at 
a temperature of — 4° it crystallizes in cubes: its specific 
gravity is -873. 

By distilling alcohol with hydrobromic acid, or a mixture 
of phosphorus and bromine, which evolves the acid, hydro- 
bromic ether EtBr, is obtained as a volatile liquid heavier 
than water; and by substituting iodine for bromine, hydr iodic 
ether EtI is found. It is a colorless liquid, with a specific 
gravity of 1*920, and a boiling point of 160° F. These 
ethers are all decomposed by an alcoholic solution of hydrate 
of potash into alcohol and a potassium salt, EtCl+(KH)O s 
= (EtH)O s -f-KCl. By the action of potassium upon chlo- 
rohydric ether, a compound is obtained in which K replaces 
CI. It is C 4 H 5 K or EtK : this is decomposed by water into 
hydrate of potash and a volatile oily substance C 4 H 6 , to 
which the name of acetene has been given. It is the hydro- 
carbon corresponding to H a , and may be written EtII, 
Another product has been formed, which is C 8 H 10 , in which 
the second atom of hydrogen is replaced by C 4 H 5 : it is EtEt, 
and has a density corresponding to four volumes of vapor. 
The binary grouping which prevails throughout all com- 
pounds is such as to forbid the isolation of the elements 
CJItf which are always grouped with a metal, chlorine, or 




even another equivalent of themselves, so that the la** of 
divisibility is never violated. 

724. Nitric Ether N(Et)0 6 =N(C 4 H s )0 6 .— The action of 
alcohol and nitric acid is violent and irregular, the alcohol 
being oxydized at the expense of the oxygen of the acid, and 
several compounds formed ; but the addition of a little urea 
or nitrate of ammonia to the mixture of the acid and alcohol 
prevents this, and the ether is then formed and distilled over 
by the aid of heat ; water being the only other product. Nitric 
acid N0 5 H0 = NHO fl -f (EtH)O a = NEtO e +H 9 O a . It is a 
colorless liquid of a sweet taste, is heavier than water, in which 
it is insoluble, and boils at 185° F. Its vapor explodes by heat. 

725. Nitrous Ether, or Hyponitrie Ether, N(Et)0 4 = 
C 4 H 5 N0 4 . — When nitric acid acts upon starch, copious red 
vapors are evolved, which are anhydrous hyponitrie acid NO s : 
they are rapidly absorbed by dilute alcohol, with the produc- 
tion of sufficient heat to cause the new ether to distil over, when 
it is condensed by means of ice. Hyponitrie acid NO s HO= 
NH0 4 +(EtH)0 a =N(Et)0 4 +H fl a . The hyponitrie ether 
is a pale yellow liquid, having a fragrant odor of apples : it boils 
at 62°, and has a specific gravity of -947. It is one of the pro- 
ducts of the action of nitric acid with alcohol, when urea is 
not added; and a solution of the impure product in alcohol, 
obtained by distilling alcohol with nitre and sulphuric acid, 
constitutes the sweet spirits of nitre of the old chemists, which 
is still used in medicine. If a mixture of nitric acid and alco- 
hol is distilled with the addition of turnings of metallic cop- 
per, pure nitrous ether may be obtained. Nitrous ether 
undergoes a remarkable decomposition by the action of 
sulphuretted hydrogen : the gas is rapidly absorbed, with the 
separation of sulphur, and alcohol, water, and ammonia are 
formed ; C 4 H 5 N0 4 +3H a S a = S fl +H a O a +C 4 H 6 0+NH 3 . 

Perchloric ether is obtained by an indirect process as an 
oily liquid, heavier than water, having a sweet, pungent taste, 
like oil of cinnamon. It explodes by slight friction, heat, 
or percussion, with fearful violence. Perchloric acid being 
C10 7 HO == C1H0 8 , the ether is C1(C 4 H 5 )0 8 . Like the nitric 
and hyponitrie ethers, it is decomposed by an alcoholic solu- 
tion of hydrate of potash into alcohol and a perchlorate. 

Sulphovinic Acid. 

726. When sulphuric acid, mixed with its weight of 
alcohoi, is heated to boiling, combination ensues with the 




elimination of water, and sulphovinic acid is formed; sul- 
phuric acid S ? H fl 8 +(EtH)0 a =S a (EtH)0 8 +H s a . By 
diluting the mixture with water and saturating it with car- 
bonate of lime, the free sulphuric acid is converted into 
insoluble sulphate of lime, and the soluble sulphovinate ia 
obtained by evaporating at a gentle heat and cooling, ia 
colorless prisms. As the carbohydrogen elements have re- 
placed one equivalent of hydrogen in the sulphuric acid, the 
new acid is monobasic, and the lime salt is S a (EtCa)0 8 
-j-H a O a : this water of crystallization is lost in a dry atmo- * 
aphere. By substituting carbonate of baryta for lime, the 
baryta salt S a (EtBa)0 8 is obtained in fine crystals; from 
this salt, by double decomposition, the sulphovinates of 
other bases may be obtained. Dilute sulphuric acid preci- 
pitates all the baryta from the baryta salt, and sulpho- 
vinic acid, S a (EtH)0 8 is obtained in solution : when concen- 
trated in vacuo it forms a syrupy liquid, which is decomposed 
by heat into alcohol and sulphuric acid, by taking up the 
elements of water. The lime and baryta salts undergo, in 
part, a similar decomposition by boiling, and after several 
years, even at the ordinary temperature, are changed into 
sulphates and alcohol. 

With hydrate of potash a similar change takes place by 
heat, and alcohol and a sulphate are formed. Sulphovinate 
of potash S a (KEt)0 8 +rKH)0 a ==S a K a 8 +(EtH)0 a ; or . 
neutral sulphate of potasn and alcohol. If the hydro-sul- 
phuret of potash KS.HS = (KH)S a is employed, sulphur- 
alcohol (EtH)S a is formed by a similar reaction ; and with any 
salt, like the acetate of potash C 4 H 8 K0 4 , a compound is ob- 
tained, in which Et replaces K : it is C 4 H 8 (Et)0 4 , or acetio 
ether. In this way the perchloric and many other ethers 
are formed by double decomposition. 

727. When carefully dried sulphovinate of potash is dis- 
tilled with a mixture of potassio alcohol (EtK)O a> sulphate 
of potash is formed, and a volatile liquid distils over, ia 
which the second atom of H ia replaced by the elements 
C 4 H 5 . S a (EtK)0 8 +(EtK)0 a =S a K a 8 +(EtEt)0 a . This 
compound is also obtained when, within certain limits of tem- 
perature, sulphovinic acid acts upon alcohol; S 8 (EtH)0 8 
+(EtH)0 a =S a H a 8 +(EtEt)0 a being the products. The 
result of this complete substitution may be conveniently 
designated as hydrovinic ether, precisely as alcohol is hydro- 
vinic acid. It has long been known in the history of tho 

Digitized by VjOOQ IC 


Bcience under the simple same of ether, which has since been 
extended to a great number of allied products, and has 
become a generic term. It is a colorless, limpid, volatile 
liquid, and as its vapor is very combustible, should never 
be brought near a flame. It has a specific gravity of -725, 
and boils under the ordinary pressure of the atmosphere at 
96° F. : by its rapid spontaneous evaporation it produces 
great cold. It is sparingly soluble in water, and the ether 
of the shops, which often contains alcohol, may be purified 
by agitation with its volume of water, which dissolves the 
alcohol, while the ether floats upon the surface. Although 
in the liquid state it is lighter than alcohol, its vapor is 
much heavier. The density of ether vapor is 2556-3 ; four 
volumes then equal 10227*2, and contain two equivalents, or 
eight volumes of alcohol, minus one equivalent, or four vo- 
lumes of water : 

2 equivalents of alcohol vapor, 2 X 6357-6 — 12715'2 

1 equivalent of water H,0 9 — 2488-0 

1 equivalent, or fonr volumes of ether vapor =\ 10227*2 

1 volume of ether vapor 2556*3 

Its equivalent is therefore 2C 4 H O a =C 8 H la O 4 — ^0,= 
C 8 H 10 0„ or Et a O a . 

728. Ether is used in the arts and in many chemical pro- 
cesses as a solvent; and in medicine, internally as a stimu- 
lant, and externally as a refrigerant, from the cold produced 
by its evaporation. An important application was some years 
since pointed out by Dr. Charles T. Jackson, of Boston, and 
introduced into practice by Mr. Morton, a dentist of that 
city : it depends upon the fact that the vapor of ether, when 
mixed with atmospheric air and inhaled, produces a kind of 
intoxication, followed by a state of stupor, in which it was 
found by these gentlemen that the subject is so far insensi- 
ble to external impressions, as to undergo the most difficult 
surgical operations without pain. This important discovery 
has been very extensively applied both in this country and 
in Europe •* and the vapor of several other liquids has been 
found to produce similar effects. 

729. In the manufacture of ether on a large scale, the 
reaction of sulphoviDic acid and alcohol is employed. When 

* The French government, in token of the high importance of the dis- 
covery, has bestowed upon Dr. Jackson the Cross of the Legion of Honor. 





the mixture of alcohol and sulphuric, acid containing sul- 
phovinic acid and water, is diluted, so as to boil much 
below 300° F., it is, as we have already shown, decomposed 
again into sulphuric acid and alcohol ; but at about 300° F., 
the sulphovinic acid reacts upon a second equivalent of 
alcohol instead of an equivalent of water, and yields sul- 
phuric acid and ether. By an ingenious method, the alter- 
nate formation and decomposition of sulphovinic acid may 
be made to furnish an unlimited supply of the new pro- 
duct. The arrangement is represented in the fig. 413. 
A mixture of five parts of alcohol of 90 per cent, and 

Fig. 413. 

eight parts of ordinary sulphuric acid is placed in the 
flask e, through the cork of which passes a thermometer t, 
and two tubes, one of which d 9 conveys the vapors away to 
a condenser B, while the other a, which dips below the 
surface of the liquid, is arranged to supply pure alcohol 
from a reservoir E. The mixture is now raised to its boil- 
ing point, which is about 300° F., and carefully maintained 
at that temperature, so as to be in constant ebullition. Al- 
cohol is slowly admitted through the cock f 9 in sufficient 
quantity to preserve the original level of the liquid in the 
flask. In this way, as the sulphovinic acid meets with the 




alcohol, it is decomposed into ether and sulphuric aciJ, but 
this reacting upon another portion of alcohol, forms water, 
which is volatilized, and a new portion of sulphovinio acid, 
to be decomposed in its turn. The ether and water distil 
over and are condensed together; and the same portion of 
sulphuric acid will serve to convert an indefinite quantity 
of alcohol into water and ether; a trace only of the sul- 
phuric acid passes over. The ether is decanted from the 
water, and purified by distilling from a small quantity of 
hydrate of potash. 

730. As it has long been obtained by the distillation of 
sulphuric acid with alcohol, it was formerly called sulphu- 
ric ether, a name which is still sometimes retained. The true 
sulphuric ether, which corresponds to the other neutral ethers, 
is obtained by the action of anhydrous sulphuric acid 
upon hydric ether. It is a neutral, dense, oily fluid, and 
differs from sulphovinic acid in having the second equiva- 
lent of H replaced by Et, its formula being S 9 (Et s )0 8 . Bv 
heat it is decomposed, in the presence of water, into sul- 
phovinic acid and alcohol. 

731. Compounds have been obtained which correspond 
to ether in which O a is replaced by sulphur, selenium, and 
tellurium. The sulphur compound is C 8 H 10 S 9 or Et^ and 
is obtained by the action of hydrochloric ether upon sul- 
phuret of potassium 2EtCl+K 8 S f = 2KCl-fEt 9 S 8 : with 
bisulphuret of potassium, a compound is obtained which is 
E^S^ and corresponds to persulphuret of hydrogen H 9 S 4 . 
These are volatile liquids, insoluble in water, and having 
a strong odor like garlic. 

732. Phosphoric acid yields several compounds contain- 
ing the elements of alcohol. The tribasic acid is P0 5 .3HO 
= PH 8 8 , and the neutral phosphoric ether is P(Et 8 )0 8 . 
The other two compounds are P(Et 9 H)0 8 and P^EtHJOg, 
and are respectively monobasic and bi basic vinic acids. 
Carl: Dvinate of potash is obtained when carbonic acid gas 
is passed into a solution of hydrate of potash in pure alcohol. 
The acid being C 9 H 3 fl , the new salt is C 2 (EtK)0 B . The 
acid has not been isolated. The true carbonic ether is 
C a (Et a )0 6 =C 10 H 10 B . By substituting bisulphuret of car- 
bon for carbonic acid gas in the above process, carbovinates 
are obtained in which the oxygen is in part replaced by 
sulphur. The acid is obtained in a separate form, and is 





0,(EtH)(O a S 4 ) ; from the yellow color of Home of its salts, 
it has been called xanthic acid. 

733. Silicic Ethers. — The action of chlorid of silicon 
upon alcohol yields two silicic ethers. They are odorous, 
pungent, and volatile liquids, which are rapidly decomposed 
by alkalies, like the other ethers, and slowly by water alone ; 
when exposed to moist air, in imperfectly closed vessels, they 
evolve alcohol and are gradually decomposed, leaving hy« 
drated silicic acid in beautiful transparent masses, resem- 
bling rock crystal. The formula of one is represented by 
C 19 H 15 Si0 8 which corresponds to a tribasic silicic acid 
Si0 8 .3HO = SiH 8 6 , and is Si(Et 8 )0 6 . The other is 
C 8 H 10 Si 4 14 , which represents a bibasic acid 4Si0 8 -|-H 8 O f 
=Si 4 H 8 14 ; the ether being Si 4 Et 8 14 . 

Chlorid of boron with alcohol yields two similar ethers : 
they burn with the fine green flame characteristic of boracic 
acid. Boracic ether is formed when alcohol is distilled from 
boracic acid, and is the cause of the green flame of an alco- 
holic solution of the acid. 

734. Olefiant Gas, C 4 H 4 . — When alcohol is mixed with 
so much sulphuric acid that the mixture does not boil 
below 320° F., the sulphovinic acid which is formed, 
undergoes a decomposition different from those already de- 
scribed ; it breaks up directly into sulphuric acid and ole 
fiantgas, S a (C 4 H 5 H)0 8 = S 3 (H a )0 8 +C 4 H 4 . 

A more elegant way of preparing it is by an arrange- 
ment similar to that used for pro- 
ducing ether. Sulphuric acid is 
diluted with nearly one-half its 
weight of water, so that its boil- 
ing point is between 320° and 
330°, and being heated in the flask 
a (fig. 414) to ebullition, the vapor 
of boiling alcohol is introduced 
from the flask d by the tube b, 
which dips a little way in the acid. 
In this process, we may suppose 
that sulphovinic acid is formed 
with the escape of an equivalent 
of water in vapor, and is then im- 
mediately decomposed into sul- 
phuric acid and olefiant gas; an 
equivalent of alcohol yields C 4 H 4 -f-H fl a . 

Fig. 414. 

The gas is thai 




obtained quite pure, and the process may be continued for 
any length of time. This compound is a product of the 
destructive distillation of many organic substances, and is 
abundant in the gases for illumination prepared by the 
decomposition of coal and the fat oils. 

735. When mingled with its own volume of chlorine 
combination ensues, and the product condenses as a heavy oily 
liquid of a sweet pungent taste. It was discovered by an 
association of Dutch chemists, who, from this reaction, 
gave to the carbohydrogen the name of oleficmt gas. It is 
C 4 H 4 C1 S , and corresponds to a carbohydrogen C 4 H e , identical 
in composition with ace ten. By the action of chlorine a series 
of compounds is formed by successive substitutions ; we have 
C 4 H 8 C1 8 , C 4 H 8 C1 4 , C fl HCl 5 and C 4 C1 6 . A similar series of com- 
pounds is obtained from chlorohydric ether, which, though re- 
presented by the same formulas, are unlike in their properties : 
the two series afford an interesting case of metamerism. 

The final product of the action of chlorine upon both 
series of compounds is the chlorid of carbon C 4 C1 6 . This 
is a white crystalline solid, with an aromatic odor, like cam- 
phor; it melts at 320°, and, at a temperature a little above 
this, may be distilled unaltered. It is scarcely combustible, 
and is unchanged by acids or alkalies. When its vapor is pas- 
sed through a porcelain tube heated to redness, it is resolved 
into chlorine gas and a new compound C 4 C1 4 , which is 
a volatile liquid, of the specific gravity of 1*65. If the 
vapor of this compound is passed repeatedly through a tube 
at a bright red heat, it is decomposed into chlorine and 
C 4 Cl r This body forms soft, silky crystals, which are vola- 
tile and combustible. 

The name of etlierilen has been applied to the type C 4 H e , 
metameric with aceten, and etheren to olefiant gas. The 
derivatives will be monochloric, bichhric etheren, &c. 

BvcMoric ether Hen, by the action of an alcoholic solution 
of hydrate of potash, yields chlorid of potassium and mono- 
chloric etheren C 4 H 8 C1 : the same way, trichloric etherilen 
gives CaHgCl,,; and sexchloric aceten C 4 C1 6 , with hydrosuk 
phuret of potassium, yields C 4 C1 4 . 

Products of the Oxydation of Alcohol. 

736. Aldehyd or Acetol, C 4 H 4 a . — The action of oxyd- 
ising substances removes H fl from alcohol and yields 





aldehyd.* It is formed, together with nitrous ether, when 
nitric acid acts upon alcohol. One equivalent of nitric 
acid NHO fl +0 4 H 6 3 =H 3 O f +NH0 4 +C 4 H 4 O a ; besides 
aldehyd, water and nitrous acid are the products, the latter 
of which forms an ether with another portion of alcohol. 
Aldehyd is best obtained by the aid of chromic acid act- 
ing upon alcohol. For this purpose an apparatus may be 
constructed like fig. 415, entirely of glass, which will be 

Fig. 415. 

found very useful for the distillation of numerous volatile 
products in organic chemistry. Equal weights of pow- 
dered bichromate of potash and strong alcohol are introduced 
into the flask a, and 1} parts of sulphuric acid are gradu- 
ally added by the safety tube s. Much heat is produced 
by the mixture, and the distillation commences at once, but 
is continued by a gentle lamp-heat under the sand-bath of 
o. . The condensing tube t is of glass, and iced water from 
the reservoir n enters and escapes by the two glass tubes 
iy Vj the former of which has a funnel mouth. 
The impure product is mixed with ether and satu* 

* Whence its name, from alcohol dehydrogcnatu* 

Digitized by VjOOQ iC 


rated with ammonia, when a compound of aldehyd and 
ammonia separates in fine crystals. This, decomposed by 
dilute sulphuric acid, affords pure aldehyd, as a colorless 
liquid having a suffocating ethereal odor. It boils at 70° F., 
and has a specific gravity of *790 : it mixes readily with 
water, and, when heated with a solution of potash, becomes 
brown and deposits a resinous substance. 

The abstraction of H a seems to have been made from the 
group C 4 H 5 , and CgIL appears in acetoi to play the same 
part as C 4 H 5 in alcohol. Thus, with potassium a com- 
pound is formed which is (C 4 H V K)CL, and the crystalline 
compound with ammonia is C 4 H .0 s +NH 8 = (C 4 H 8 .NH 4 )0j, 
in which NH 4 replaces H. When a solution of aldehyd is 
added to one of ammoniacal nitrate of silver, the metal 
is reduced and lines the vessel with a brilliant film of sil- 
ver. A similar process has been successfully applied to the 
manufacture of mirrors. 

737. Aldehyd cannot be preserved unchanged, even in 
sealed tubes, but is slowly changed into two polymeric com- 
pounds. One of these, elaldehyd, is a dense oily fluid, 
which has none of the properties of aldehyd. The density 
of its vapor is three times that of aldehyd ; and its formula 
is 3C 4 H 4 9 = C^H^Og. The other body, metaldehyd, forma 
hard white prisms ; it is formed by the union of four equiva- 
lents of aldehyd, and is C 16 H t6 9 . Aldehyd is also ob- 
tained as a product of the decomposition of lactic acid or 
lactate of copper by heat, and is formed in large quantity 
when a lactate is distilled with binoxyd of manganese and 
sulphuric acid. When the isomerism of lactic acid with 
glucose is considered, it is easy to understand that while the 
latter is decomposed by fermentation into carbonic acid and 
alcohol, lactic acid by oxydation may yield carbonic acid 
and aldehyd. We shall see, farther on, that it is possible 
to reproduce lactic acid from aldehyd. 

738. Chloral. — By the prolonged action of chlorine upon 
alcohol a liquid is obtaiued, to which the name of chloral 
has been given. It is aldehyd in which chlorine replaces 
H 3 , and is represented by C 4 (IIC1 3 )0 2 . 

Sulphur aldehyd C 4 H 4 S 3 has also been obtained, and 
both the trichloric and sulphuretted species yield polyme- 
ric modifications similar to those of normal aldehyd. The 
action of sulphuretted hydrogen upon an aqueous solution 
of aldehydate of ammonia produces large transparent crys- 




tals of an organic base, named thialdine. It is slightly 
soluble in water, but dissolves readily in alcohol and ether : 
the crystals are very fusible and volatile, and may be dis- 
tilled with the vapor of boiling water. The formula of 
thialdine a C lfl H 13 NS 4 : it corresponds to an amid of the 
trimeric modification of sulphuretted aldehyd C^H^Sg. 
This base has no alkaline reaction, but forms beautifully 
crystalline salts. A corresponding compound, in which 
selenium replaces sulphur, has been formed, but is very 

A mixture of bisulphuret of carbon with an alcoholic 
solution of aldehydate of ammonia deposits sparingly 
soluble crystals of a new base, called carbo-thicddine, which 
is represented by C^H^N^S^ It contains the elements of 
two equivalents of aldehyd, and its formation is thus re- 
presented : 2C 4 H 7 NO a +C 9 S 4 =2H fl 9 +C 10 H 10 N fl S 4 . 

739. Acetic Acidy C 4 H 4 4 . — When aldehyd is exposed 
to the air it absorbs 0, and is converted into acetic acid 
C 4 H 4 f +0 a =C 4 H 4 4 . If a mixture of hydrate of potash 
and lime be moistened with alcohol and exposed to heat, 
hydrogen gas is evolved, and an acetate formed, C 4 H 6 O a -t- 
KH0 ft =C 4 H 8 K0 4 +H 4 . 

740. Pure alcohol undergoes no change when exposed to 
the air alone ; but if its vapor mixed with air is brought into 
contact with platinum-black, it slowly unites with oxygen 
to form aldehyd, which readily absorbs another portion of 
oxygen and produces acetic acid. The oxydating power of 
finely-divided platinum has been before alluded to ; it ab- 
sorbs or condenses great quantities of gases and vapors in 
its pores, where they appear to be brought together in such 
a state that they readily react upon each other. 

741. The formation of acetic acid may be beautifully 
shown by placing a little platinum-black in a watch-glass, by 
the side of a small vessel of alcohol, covering the whole 
with a bell-glass, and setting it in the sunlight. In a short 
time the vapor of acetic acid will condense on the sides of 
the glass, and run down in drops; and if we occasionally 
admit fresh air by raising the bell-jar, the whole of the 
alcohol will be acidified in a few hours. 

In the ordinary process for vinegar, alcoholic liquors, as 
wine and cider, are exposed to the air in open vessels. 
Although a mixture of pure alcohol and water does not 
absorb oxygen from the air, a small portion of any ferment, 




as vinegar, already formed, or the fungus plant 
called mother of vinegar, enables it to com- 
bine with oxygen. In this process the essen- 
tial thing is a free supply of air and a propei 
1 temperature. In the manufacture of vine- 
gar on the large scale, this is secured by 
causing the liquor (b, fig. 416) to trickle from 
threads of cotton arawn through holes, over 
shavings of beech-wood previously soaked in 
Fig. 416. vinegar, and contained in a large cask with 
holes in its sides, (c c c c,) so as to admit a free circulation 
of air. In this way a vast surface is exposed, and the ab- 
sorption of oxygen is very rapid, causing an elevation of 
20° or 30° in the temperature. The liquid is passed through 
this apparatus four or five times in the course of twenty-four 
hours, in which time the change of the alcohol into vinegar is 
generally complete. The product is collected in the vessel a. 

742. Acetic acid is also obtained by distilling wood in 
close vessels, (712,) a process employed on a large scale for 
the preparation of the acid. The products are, besides car- 
bonic acid and carburetted hydrogen, a large quantity of 
acetic acid mixed with oily and tarry matters, from which 
it is separated mechanically. The acid thus prepared is 
known as pyroliyneow acid, and is largely used in the arts 
of dyeing and calico-printing ; but being contaminated by 
empyreumatic oils, is not fit for the purposes of domestic 
economy. By combining it with bases, salts are obtained, 
which, when decomposed, afford a pure acid. 

743. By distilling dried acetate of soda with strong sul- 
phuric acid, a very concentrated acid is obtained, which, 
when exposed to cold, deposits crystals of pure acetic acid 
C 4 H 4 4 . The pure acid is solid below 60° F. \ when liquid, 
it has a specific gravity of 1063, and boils at 248°. It is 
perfectly soluble in water, alcohol, and ether ; it has a pun- 
gent fragrant odor and a very acid taste, and, when applied 
to the skin, is highly corrosive. The acid is monobasic ; all 
its salts are soluble in water. 


744. Acetate of potash C 4 H 3 (K)0 4 is easily prepared by 
neutralizing acetic acid with carbonate of potash. It is a 
very soluble deliquescent salt, and is employed in medicine. 




Acetate of soda C 4 H 8 (Na)0 4 forms large crystals with six 
equivalents of water. It is prepared in large quantities from 
pyroligneous acid; the salt is heated to destroy the oily 
matters, and then affords by its decomposition a pure acid. 
Acetate of ammonia C 4 H 4 4 +NH 8 = C 4 H s (NH 4 )0 4 is 
used in medicine by the name of the spirit of Mindereus. 
It is prepared by saturating acetic acid with ammonia, and 
is exceedingly soluble and volatile. The acetate of zinc is a 
beautiful white salt, and is employed as a tonic and astrin- 
gent. The acetate of alumina C 4 H s (al)0 4 is much used in 
dyeing; it is obtained by decomposing a solution of alum by 
one of acetate of lead ; sulphate of lead precipitates, and 
acetate of alumina with acetate of potash remains in solu- 
tion. The protacetate and peracctate of iron are prepared in 
a similar manner, and are largely employed in calico-print- 
ing and dyeing. They are represented by C 4 (H,Fe)0 4 , and 
C 4 H 3 fe0 4 . (See § 649.) 

745. Acetate of Lead, C 4 H 8 (Pb)0 4 .— This salt is well 
known under the name of sugar of lead. It is prepared by 
dissolving oxyd of lead (litharge) in acetic acid, and crystal- 
lizes with three equivalents of water, which are expelled by 
gentle heat. It is a white salt, with a very sweet and astrin- 
gent taste, and is often employed as a medicine ; but is poi- 
sonous, and should be used internally with caution. 

The acetate of lead has a great tendency to combine with 
oxyd of lead, with which it forms several definite compounds. 
These are generally designated as basic salts, but should be 
carefully distinguished from the salts containing more than 
one equivalent of base, which are formed by bibasic and 
tribasic acids. In these last, the metal replaces the hydro- 
gen of the acid, but in the basic acetates the neutral salt com- 
bines directly with the oxyd. To distinguish them, the term 
surbasic is applied, and the compound of the acetate with 
an equivalent of oxyd of lead is called the surbasic acetate 
of lead. Three of these compounds are known, in which 
the acetate is combined with one-fourth, one, and two and a 
half equivalents of oxyd. The second is the only one of 

746. Surbasic Acetate of Lead, C 4 H s Pb0 4 +Pb a a — 
This salt, commonly called the tribasic acetate, is obtained 
by digesting a solution of six parts of the acetate with seven 
of litharge ; the oxyd is dissolved, and the liquid affords, by 
evaporation, a salt crystallizing in long needles. It is also 




slowly formed when metallic lead is digested in an open 
vessel with a solution of the acetate, oxygen being absorbed 
from the air. The salt is very soluble in water, and its 
solution has an alkaline reaction ; it is known in pharmacy 
as Goulard! % extract, or solution of lead. When exposed 
to the air, it absorbs carbonic acid, and the equivalent 
of oxyd of lead is precipitated as a carbonate. This reaction 
enables us to explain the formation of white-lead. 

747. A process frequently employed is to mix litharge 
and about X J^ of sugar of lead into a thin paste with water? 
the mixture is gently heated, and a current of carbonic acid 
is passed through it. The acetate of lead dissolves a portion 
of the oxyd to form the tribasic salt ; this is immediately 
decomposed by the carbonic acid, which precipitates car- 
bonate of lead, and leaves the acetate free to dissolve a new 
portion of oxyd. In this way the smallest quantity of the 
acetate is able to convert a large portion of the oxyd into 
carbonate, and at the end of the process to remain unaltered. 

748. In the ordinary process, the plates of lead are ex- 
posed to the action of acetic acid, moisture, air, and the car- 
bonic acid from fermenting tan, (588.) The lead immedi- 
ately becomes covered with a film of oxyd by the action of 
the air. This is dissolved by the vapor of the acetic acid, 
and forms a solution of neutral acetate, which moistens the 
plates and gradually acts upon them, forming, by the aid of 
the atmospheric oxygen, the basic acetate, which is decomposed 
by tbc carbonic acid, in the same manner as in the last process, 
and the neutral acetate is again set free to act upon the me- 
tallic lead ; the process goes on until all the lead is carbon- 
ated. In this way a small quantity of acetic acid will, 
under favorable circumstances, convert a hundred times its 
weight of lead into carbonate in a few weeks. 

749. Acetate of Copper, C 4 H 8 (Cu)0 4 .— This salt is very 
soluble, and forms beautiful green crystals of the monoclinic 
system, containing one equivalent of water. The acetate of 
copper forms several surbasic salts which are insoluble in 
water. The fine green pigment called verdigris is a mix- 
ture of two or more of these : all of these copper salts are 
very poisonous. The acetate of silver C 4 H 3 ( Ag)0 4 crystal- 
lizes in white scales, and is the least soluble of the acetates. 

750. Ofiloracetic Acid, C 4 C1 3 (H)0 4 .— We have already 
mentioned this product of the action of chlorine upon 
erystallizable acetic acid; one equivalent of the aoid and 




three of chlorine yield three of chlorobydric acid and 
one of the new compound, C 4 H 4 4 +3C1 8 =C 4 C1 3 (H)0 4 
-f-3HCl. The chloracetic acid is very soluble, but may be 
obtained in fine rhombohedral crystals ; its salts resemble 
the ordinary acetates. When an amalgam of potassium 
is added to a solution of chloracetate of potash, chlorid of 
potassium, hydrate of potash, and the normal acetate of 
potash are formed. In this reaction water intervenes, and 
we may suppose that the alkaline metal, decomposing water, 
forms 3(KH)0 9 and 3KH, which last, reacting with the 
chloracetate, would form chlorid of potassium, leaving H s in 
place of the chlorine. 

Acetic Ether y C 4 H 8 (Et)0 4 ==C 9 H 8 4 .— This ether is form- 
ed by the direct action of acetic acid upon alcohol, but is best 
obtained by diotilling a mixture of five parts of acetate of 
soda, eight of sulphuric acid, and three of alcohol. It is a 
very fragrant and volatile liquid, soluble in seven parts of 
water. The odor of wine- vinegar is due to the presence of a 
little acetic ether. It contains, like the ethers of other mo- 
nobasic acids, the elements of the acid and the alcohol minus 
an equivalent of water H 9 8 . The ethers like this, formed by 
the acids of the type C n H w 4 with their respective alcohols, 
are polymeric of the corresponding aldeydes ; acetic ether 
equals 2xC 4 H 4 9 .. 

Acetic ether is dissolved by a concentrated solution of am- 
monia, and the solution affords by evaporation a white crys- 
talline substance, very volatile and fusible, to which the name 
of acetamid has been given ; it is the amid of acetic acid, 
and contains the elements of acetate of ammonia less an 
equivalent of water : C 4 H 3 (NH 4 )0 4 = C 4 H ? N0 4 = H 9 9 + 
C 4 H 5 N0tf which is the formula for acetamid. In its form- 
ation from the ether, alcohol is set free; acetic ether 
C 8 H 6 4 + NH 8 = C 4 H fl 9 + C 4 H 5 N0 9 . The ethers of 
almost all acids yield amids by a similar reaction. When 
heated gently with potassium, acetamid evolves a gas and 
yields cyanid of potassium C 9 KN. 

If acetamid is distilled with anhydrous phosphoric acid, 
the elements H 9 9 are abstracted from it, and a volatile 
liquid is obtained, which is C 4 H 5 N0 g — H 9 9 ==C 4 H 8 N. It 
has received the name of acetonitryl. By the action of 
strong acids and alkalies both of these compounds regenerate 
ammonia and acetic acid. 

751. When an acetate is heated with an excess of hydrato 





of potash, it breaks up into carbonate of potash and a carbo- 
hydrogen C g H 4 . Acetate of potash C 4 H g K0 4 +(KH)0 fl = 
C s K g O 6 -f-0 v fi 4 . It has already been described under the 
name of marsh gas, from its occurrence in marshes, as a 
product of the decomposition of vegetable matter. To indi- 
cate its relations in the organic series, the name of formen 
has been given to it. The chloracetates undergo a similar 
decomposition, and yield trichloric formen C^Cytt, in which 
Gl s replaces H r The chloracetate of ammonia is decom- 
posed by boiling with an excess of ammonia, into carbonate 
and this chlorinized species. 

752. When an acetate is decomposed by heat, or when 
the vapor of acetic acid is passed through a red-hot tube, the 
acid undergoes a peculiar decomposition; two equivalents 
of it unite with the elimination of one equivalent of carbonic 
acid, C.H.0 6 .2 XC 4 H 4 4 =C 8 H 8 8 — C a H s 6 =C 8 n fl 9 
To this liquid the name of action has been given ; by oxyd- 
izing agents, like chromic acid, it yields acetic acid. We 
have already mentioned aceton as a product of the distilla- 
tion of sugar with lime : it is accompanied with an analogous 
compound, to which the name of meiaceton has been given, 
and which corresponds to a new acid homologous with acetic 
acid, to which the name of metacetonic or propionic acid has 
been given. It is C 6 H 6 4 == C 4 H 4 4 +C 8 H fl , and is very 
much like acetic acid in its properties. When a paste of 
wheat flour is fermented with fragments of white leather 
and a quantity of chalk, propionate of lime is formed in 
large quantity. The fermentation is probably analogous to 
that which yields butyric acid. The decomposition of the 
salts of propionic acid by heat furnishes directly propion or 
metaceton, in the same way as butyric acid furnishes the 
homologue butyron. By the action of nitric acid upon 
butyron, a coupled acid is obtained, which is nitropropionio 
acid C 6 (H 5 N0 4 )0 4 =C.H 5 N0 8 . 

Methol, CJE^O,. 

753. Wood-spirit, Pyroxylin Spirit, Methylic Alcohol.*— 
This substance has already been mentioned as a product of 

* Pyroxylic spirit, from pur, fire, and xulon, wood. Methylio alcohol, 
from methu, wine, and hule, wood; signifying the wine or alcohol of wood. 
In names like kakodyl, and the terms ethyle, amyle, in the language 
of the compound radical theory, the same syllable is derived from huU, 
in its more extended sense of matter or prinoiple. 

bigitized by G00gle 

METHOL. 435 

the destructive distillation of wood. The acetic acid of the 
crude product being saturated with lime, impure methol is 
obtained by distillation, and is afterward purified by re- 
peated rectifications. It is a colorless liquid, of a peculiar 
and somewhat unpleasant odor, and a hot, pungent taste. 
It has a specific gravity of -798, and boils at 152° ; it ia 
very combustible, and burns with a pale blue flame. Like 
alcohol, it mixes in all proportions with water. It is occa- 
sionally used in the arts for dissolving resins and making 
varnishes, and the pure wood-spirit has lately acquired 
some celebrity in